Pull kvm updates from Paolo Bonzini:
"ARM64:
- Add support for 'slot' based PMU events, paired with new UAPI that
compels the user to select a specific PMU implementation
- Lazy save/restore of vCPU state for pKVM, along with various fixes
and cleanups to the management of vCPU state between the untrusted
host and pKVM hypervisor
- Disable traps of EL1 registers for nested hypervisors when
FEAT_NV2p1 is present, guaranteeing that EL2-specific register bits
are stateful in the EL1 counterpart
- Leverage FEAT_NV3 to avoid unnecessary ERET/TLBI traps when the
scope of those instructions remains 'in host' (i.e. L1
kernel/userspace)
- Pile of fixes for the management of the VNCR pseudo-TLB, such as
under-invalidations and races with concurrent TLBIs on other vCPUs
- Consolidate the non-protected and pKVM view of ICH_VTR_EL2 to a
runtime-patched constant, allowing the same data to be shared with
pKVM prior to dropping host privileges
- Considerable pile of LLM-assisted fixes around the shop but mostly
in the VGIC, our in-kernel generator of bugs (and sometimes
interrupts)
LoongArch:
- Advertise already-supported capabilities
- Some bug fixes about timer and MMIO
- Some hardening about interrupt injection
- Replace kvm_err() with kvm_pr_unimpl()
- Add FPU/LSX/LASX test cases for selftests
RISC-V:
- Svadu/Zicfiss/Zicfilp FWFT support for Guest
- Use try_cmpxchg for IMSIC MRIF RMW
- More arch-specific tracepoints in KVM RISC-V
- Eager page splitting when enabling dirty logging
- Optimize hfence request handling for SMP Guests
- Improve dirty log clearing by skipping zero bits in mask
- Guard HFENCE range loops against overflow
- CPU PM notifiers in KVM RISC-V for non-retentive idle states
- Fix kernel-mode vector context save/restore for Guest
s390:
- Fixes for vfio-ap
- Fixes for the gmap rework
- Fixes for vsie
- AI triggered fixes all over
- diag9c tracing
- code move preparation for the additional arm64 support
- enable CONTEXT_ANALYSIS
x86:
- Perform spring cleaning on x86.{c,h} and asm/kvm_host.h, by adding
regs.c (the kvm_cache_regs.h => regs.h is already applied) and
msrs.{c,h}, and moving relevant code out of x86.c
- Split kvm_mmu in three parts, respectively to describe the format
of page tables, walking the guest page tables and building the page
tables. Always use the same page table walker kvm->arch.gva_walk as
the entry point to convert a guest's virtual address, where the
previous code used two different kvm_mmu structs depending on
whether the walk included nested EPT/NPT or not. Make page fault
vmexits reuse the permission checking machinery that is used for
guest page faults. This is both a cleanup and a baby step towards
supporting XS/XU memory permissions
- Document some of the "fun" gotchas with the APIC base when creating
IRQCHIPs on x86
- Remove a defunct masterclock update from kvm_xen_shared_info_init().
It could result in incorrect kvmclock due to triggering an
unnecessary switch to/from masterclock mode
- Skip Xen runstate time updates if time has effectively gone
backwards, so that the guest doesn't report 100% steal time for
a very, very long time
- Drop KVM's runtime updates of the Xen PV timing CPUID leaf, as KVM
was updating the wrong sub-leaf, and upstream KVM will soon provide
all the information needed by userspace to populate the CPUID field
itself
- Fix a bug where KVM would walk a newly created rmap without holding
the rmap lock (or mmu_lock) during aging
- Fix a bug where aging TDP MMU SPTEs could clobber FROZEN SPTEs
- Fix a variety of #DB priority bugs
- Fix a class of races related to enabling Hyper-V emulation on a
vCPU after the vCPU is visible to the rest of KVM
- Use static calls for nested virtualization ops
- Move more KVM-internal code out of x86's kvm_host.h
- Enumerate support for a variety of Zhaoxin instructions that don't
require explicit virtualization
- Fix missing EFER validation bugs, including in the KVM_SET_SREGS*
path
- Harden kvm_vcpu_map() against double-mapping and thus leaking
references
- Misc fixes and cleanups, e.g. for largely benign syzkaller splats
x86 (Intel):
- Zero a vCPU's entry in VMX's Posted Interrupt Descriptor table used
for IPI virtualization when the vCPU is freed, to fix a
use-after-free where hardware will write to a freed vCPU's PID
- Service local TLB flushes on a failed nested VM-Enter to fix a bug
where KVM could miss a TLB on a future, successful VM-Enter with
the same L2 VPID
- Cap the maximum value shoved into the VMX Preemption Timer to
workaround an erratum that affects all existing Intel CPUs that
support CPUID 0x15
- Fix VPID virtualization bugs where KVM would fail to flush hardware
TLBs
- Harden the TDX "populate" ioctls against bad input, and to prepare
for supporting in-place private<=>shared conversion
x86 (AMD):
- Forcefully invalidate SNP VMSA pages if their backing guest_memfd
page is zapped/invalidated, e.g. due to a PUNCH_HOLE in response to
a Page-State Change request
- Remove a dying VM from the GA Log notifier list before the VM is
actually destroyed, to fix a potential use-after-free
- While FOLL_WRITE was needed in the past to trigger CoW unsharing,
nowadays FOLL_LONGTERM does that already even without FOLL_WRITE,
and in fact, get_user_pages() actually disallows FOLL_WRITE
together with FOLL_LONGTERM. So don't pass FOLL_WRITE when
registering encrypted memory regions, i.e. when pinning SEV/SEV-ES
guest memory, to fix a regression with file-backed memory
introduced by KVM's (correct) usage of long-term pins
(This was reviewed by mm maintainers; for more information, see
commit ee1a586dd1 "KVM: SEV: Drop FOLL_WRITE for encrypted region
registration")
- Allocate full pages for SEV/SEV-ES {DE,EN}CRYPT ops on SNP-enabled
hosts to fix a data corruption issue due to the PSP driver
assigning to-be-written pages to firmware (as required by the SNP
specs)
- Unconditionally intercept ICBEP so that KVM generates the correct
guest RIP when handling an ICEBP-induced TASK_SWITCH #VMEXIT
- Harden the SNP "populate" ioctls against bad input, and to prepare
for supporting in-place private<=>shared conversion
Generic:
- Remove kvm_debugfs_dir if kvm_init() fails after creating KVM's
debugfs
- Add a per-VM bitmap to track which vCPU IDs have been "claimed" but
for which the vCPU isn't yet online, and use the bitmap to reject
duplicate IDs before calling into arch code. This allows arch code
to consume vcpu_id without having to worry about cross-vCPU
clobbering (at least s390 and x86 have had related bugs)
- Rework the so called "prepare" and "invalidate" guest_memfd hooks
to prepare for in-place private<=>shared conversion, and clean up a
few warts along the way
Selftests:
- Automatically allocate a full page for L2 guest stacks on x86
instead of requiring test-specific L1 guest code to carve out a
portion of the L1 stack for L2 usage, and to ensure the L2 stack
also adheres to the x86-64 calling convention ABI
- Add a selftest to verify {Guest,Host}-Only behavior in x86's
mediated PMU
- Clean up nested SVM's handling of GPRs on L2<=>L1 transitions,
reuse the functionality for nested VMX, and drop the ucall hack
that was fudging around the lack of GPR switching on nVMX
- Add a stress test to verify KVM doesn't clobber/drop #PF state,
e.g. CR2, across save/restore, including when L2 is active
- Add a test to verify KVM_CREATE_VM accepts exactly what is reported
by KVM_CAP_VM_TYPES
- Misc selftests fixes and cleanups
- Fix several issues with seeding the pRNG, and rework the pRNG APIs
to that the pRNG can be sanely used in host code, not just guest
code
- Add an IRQ test to validate virtual IRQ deliverty for IRQs wired up
via KVM_IRQFD + KVM_SET_GSI_ROUTING, with optional support for
triggering IRQs via writes to an assigned VFIO device
- Add syscall wrappers to assert success on a variety of pthreads and
CPU affinity APIs
- Set vCPU pthread affinity as early as possible to reduce contention
issues that were surfaced by PREEMPT_LAZY, which result in runtimes
of over a minute on large hosts, versus the expected ~5 seconds
- Rework the PMU counters test to run each testcase using a single VM
with many vCPUs for each sub-testcase, instead of using a unique VM
for each sub-testcase. This cuts the runtime by ~20x
Miscellaneous:
- MAINTAINERS updates for vfio-ap, guest_memfd, kvm-x86. Mostly
representing the status quo more accurately, but also... welcome
David Hildenbrand as guest_memfd reviewer!"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (413 commits)
KVM: arm64: Validate GICv5 timer PPIs before claiming ownership
KVM: arm64: vgic: Reject out-of-range GICv5 PPI IDs
KVM: arm64: vgic: Prevent speculative SPI array underflow
KVM: arm64: vgic: Free gic_kvm_info on initialization failure
KVM: arm64: Avoid mismatched accesses to 'struct kvm_nvhe_init_params'
s390/vfio-ap: Fix NULL deref in status_show() during queue probe
s390/vfio-ap: Fix hot-unplug skipped when last AP adapter or domain removed
s390/vfio-ap: fix potential use of uninitialized apm_filtered bitmap
s390/vfio-ap: Fix control domain removal in vfio_ap_mdev_cfg_remove
s390/vfio-ap: Fix required lock not held during update of ap_matrix_mdev object
s390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects
s390/vfio-ap: Fix dereference matrix_mdev->kvm without checking for NULL
s390/vfio-ap: Fix stale do_remove flag across iterations in vfio_ap_mdev_cfg_remove
RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector
riscv: vector: allow non-preemptible kernel-mode vector with IRQs off
riscv: vector: refactor riscv_v_start_kernel_context
KVM: s390: gmap: Make prefix handling optional
KVM: s390: gmap: Make CMMA optional
KVM: s390: gmap: Make storage keys optional
KVM: s390: Prepare gmap for a second KVM implementation
...
Introduce a new capability and ioctl to expose CPU compatibility modes
supported by the host processor for nested guests.
On IBM POWER systems, newer processor generations (N) can operate in
compatibility modes corresponding to earlier generations, like (N-1) and
(N-2). This is particularly relevant for nested virtualization, where
nested KVM guests may need to run with a specific processor compatibility
level.
Introduce KVM_CAP_PPC_COMPAT_CAPS capability and the corresponding
KVM_PPC_GET_COMPAT_CAPS vm ioctl. The ioctl returns a bitmap describing
the compatibility modes supported by the host in respective bit numbers,
allowing userspace (e.g., QEMU) to select an appropriate compatibility
level when configuring nested KVM guests.
The ioctl handling is added in kvm_arch_vm_ioctl() and retrieves host
CPU compatibility capabilities via a PowerPC-specific backend
implementation when available.
The struct kvm_ppc_compat_caps places the 'size' field first so it can
be read alone via get_user() before copy_struct_from_user() is called,
avoiding pointer arithmetic to locate the size field.
The ioctl is defined using _IO so the ioctl number remains stable even if
the struct grows in future versions. It uses copy_struct_from_user() and
copy_struct_to_user() to provide forward- and backward-compatible
extensibility: older userspace passing a smaller struct to a newer kernel
gets zero-padded trailing fields. Newer userspace passing a larger struct to
an older kernel (usize > ksize) succeeds if trailing bytes are zero (the
kernel reports back min(usize, ksize) as the filled size); if trailing bytes
are non-zero, the kernel writes back ksize into host_caps.size and returns
-E2BIG so userspace can retry with the correct size.
KVM_PPC_COMPAT_CAPS_SIZE_VER0 is defined as a frozen integer constant
(24) marking the size of the initial struct version, used as the
minimum floor for size field validation, similar to other versioned
struct interfaces in the kernel.
The 'flags' field is reserved for future use. The kernel rejects any
call where flags is non-zero with -EINVAL, preventing garbage values
from being baked into ABI permanently.
The ioctl returns appropriate error codes: E2BIG if usize exceeds
PAGE_SIZE, or if new userspace provides a larger struct with non-zero
trailing bytes (with ksize written back into host_caps.size for the
retry); EINVAL for an invalid size or non-zero reserved fields; EFAULT
for failed copy operations; and ENOTTY if the backend doesn't implement
get_compat_caps.
Suggested-by: Vaibhav Jain <[email protected]>
Tested-by: Gautam Menghani <[email protected]>
Reviewed-by: Gautam Menghani <[email protected]>
Tested-by: Anushree Mathur <[email protected]>
Reviewed-by: Ritesh Harjani (IBM) <[email protected]>
Signed-off-by: Amit Machhiwal <[email protected]>
Signed-off-by: Madhavan Srinivasan <[email protected]>
Link: https://patch.msgid.link/[email protected]
Introduce a new vCPU feature KVM_ARM_VCPU_PMU_V3_STRICT. When set, KVM
does not create a default PMU when initializing the vCPU, and userspace
must select one explicitly via KVM_ARM_VCPU_PMU_V3_SET_PMU before the
first KVM_RUN.
The flag forces the VMM to be aware of the PMU implementation of the
guest to be created, so that certain information about the PMU becomes
deterministic (if on a heterogeneous system) and becomes safe to be
exposed to the guest. It can be used as an umbrella flag to gate future
PMUv3 UAPI changes.
When no default PMU is created, kvm->arch.arm_pmu stays NULL until SET_PMU
runs, so kvm_arm_pmu_v3_init() now refuses to run if kvm->arch.arm_pmu
is NULL.
Signed-off-by: Congkai Tan <[email protected]>
Reviewed-by: Geoff Blake <[email protected]>
Reviewed-by: Haris Okanovic <[email protected]>
Reviewed-by: Stanislav Spassov <[email protected]>
Co-developed-by: Oliver Upton <[email protected]>
Reviewed-by: Fuad Tabba <[email protected]>
Tested-by: Fuad Tabba <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Oliver Upton <[email protected]>
Add KVM_CAP_S390_HPAGE_2G to signal to userspace that 2G hugepages may
be used to back the guest; restrictions apply similar to 1M hugepages.
Enable the (for now still ignored) GMAP_FLAG_ALLOW_HPAGE_2G flag for
the guest gmap, and propagate / disable it as necessary.
Reviewed-by: Steffen Eiden <[email protected]>
Signed-off-by: Claudio Imbrenda <[email protected]>
Message-ID: <[email protected]>
KVM/arm64 updates for 7.1
* New features:
- Add support for tracing in the standalone EL2 hypervisor code,
which should help both debugging and performance analysis.
This comes with a full infrastructure for 'remote' trace buffers
that can be exposed by non-kernel entities such as firmware.
- Add support for GICv5 Per Processor Interrupts (PPIs), as the
starting point for supporting the new GIC architecture in KVM.
- Finally add support for pKVM protected guests, with anonymous
memory being used as a backing store. About time!
* Improvements and bug fixes:
- Rework the dreaded user_mem_abort() function to make it more
maintainable, reducing the amount of state being exposed to
the various helpers and rendering a substantial amount of
state immutable.
- Expand the Stage-2 page table dumper to support NV shadow
page tables on a per-VM basis.
- Tidy up the pKVM PSCI proxy code to be slightly less hard
to follow.
- Fix both SPE and TRBE in non-VHE configurations so that they
do not generate spurious, out of context table walks that
ultimately lead to very bad HW lockups.
- A small set of patches fixing the Stage-2 MMU freeing in error
cases.
- Tighten-up accepted SMC immediate value to be only #0 for host
SMCCC calls.
- The usual cleanups and other selftest churn.
LoongArch KVM changes for v7.1
1. Use CSR_CRMD_PLV in kvm_arch_vcpu_in_kernel().
2. Let vcpu_is_preempted() a macro & some enhanments.
3. Add DMSINTC irqchip in kernel support.
4. Add KVM PMU test cases for tools/selftests.
Add device model for DMSINTC interrupt controller, implement basic
create/destroy/set_attr interfaces, and register device model to kvm
device table.
Reviewed-by: Bibo Mao <[email protected]>
Signed-off-by: Song Gao <[email protected]>
Signed-off-by: Huacai Chen <[email protected]>
* kvm-arm64/pkvm-protected-guest: (41 commits)
: .
: pKVM support for protected guests, implementing the very long
: awaited support for anonymous memory, as the elusive guestmem
: has failed to deliver on its promises despite a multi-year
: effort. Patches courtesy of Will Deacon. From the initial cover
: letter:
:
: "[...] this patch series implements support for protected guest
: memory with pKVM, where pages are unmapped from the host as they are
: faulted into the guest and can be shared back from the guest using pKVM
: hypercalls. Protected guests are created using a new machine type
: identifier and can be booted to a shell using the kvmtool patches
: available at [2], which finally means that we are able to test the pVM
: logic in pKVM. Since this is an incremental step towards full isolation
: from the host (for example, the CPU register state and DMA accesses are
: not yet isolated), creating a pVM requires a developer Kconfig option to
: be enabled in addition to booting with 'kvm-arm.mode=protected' and
: results in a kernel taint."
: .
KVM: arm64: Don't hold 'vm_table_lock' across guest page reclaim
KVM: arm64: Allow get_pkvm_hyp_vm() to take a reference to a dying VM
KVM: arm64: Prevent teardown finalisation of referenced 'hyp_vm'
drivers/virt: pkvm: Add Kconfig dependency on DMA_RESTRICTED_POOL
KVM: arm64: Rename PKVM_PAGE_STATE_MASK
KVM: arm64: Extend pKVM page ownership selftests to cover guest hvcs
KVM: arm64: Extend pKVM page ownership selftests to cover forced reclaim
KVM: arm64: Register 'selftest_vm' in the VM table
KVM: arm64: Extend pKVM page ownership selftests to cover guest donation
KVM: arm64: Add some initial documentation for pKVM
KVM: arm64: Allow userspace to create protected VMs when pKVM is enabled
KVM: arm64: Implement the MEM_UNSHARE hypercall for protected VMs
KVM: arm64: Implement the MEM_SHARE hypercall for protected VMs
KVM: arm64: Add hvc handler at EL2 for hypercalls from protected VMs
KVM: arm64: Return -EFAULT from VCPU_RUN on access to a poisoned pte
KVM: arm64: Reclaim faulting page from pKVM in spurious fault handler
KVM: arm64: Introduce hypercall to force reclaim of a protected page
KVM: arm64: Annotate guest donations with handle and gfn in host stage-2
KVM: arm64: Change 'pkvm_handle_t' to u16
KVM: arm64: Introduce host_stage2_set_owner_metadata_locked()
...
Signed-off-by: Marc Zyngier <[email protected]>
Now that all the bits are properly addressed, provide a mechanism
for testing ESA mode guests in nested configurations.
Signed-off-by: Hendrik Brueckner <[email protected]>
[[email protected]: Updated commit message]
Reviewed-by: Janosch Frank <[email protected]>
Signed-off-by: Eric Farman <[email protected]>
Signed-off-by: Janosch Frank <[email protected]>
Introduce a new VM type for KVM/arm64 to allow userspace to request the
creation of a "protected VM" when the host has booted with pKVM enabled.
For now, this feature results in a taint on first use as many aspects of
a protected VM are not yet protected!
Tested-by: Fuad Tabba <[email protected]>
Tested-by: Mostafa Saleh <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Marc Zyngier <[email protected]>
Commit 94dfc73e7c ("treewide: uapi: Replace zero-length arrays with
flexible-array members") broke the userspace API for C++.
These structures ending in VLAs are typically a *header*, which can be
followed by an arbitrary number of entries. Userspace typically creates
a larger structure with some non-zero number of entries, for example in
QEMU's kvm_arch_get_supported_msr_feature():
struct {
struct kvm_msrs info;
struct kvm_msr_entry entries[1];
} msr_data = {};
While that works in C, it fails in C++ with an error like:
flexible array member 'kvm_msrs::entries' not at end of 'struct msr_data'
Fix this by using __DECLARE_FLEX_ARRAY() for the VLA, which uses [0]
for C++ compilation.
Fixes: 94dfc73e7c ("treewide: uapi: Replace zero-length arrays with flexible-array members")
Cc: [email protected]
Signed-off-by: David Woodhouse <[email protected]>
Link: https://patch.msgid.link/[email protected]
[sean: tag for stable@]
Signed-off-by: Sean Christopherson <[email protected]>
KVM generic changes for 7.0
- Remove a subtle pseudo-overlay of kvm_stats_desc, which, aside from being
unnecessary and confusing, triggered compiler warnings due to
-Wflex-array-member-not-at-end.
- Document that vcpu->mutex is take outside of kvm->slots_lock and
kvm->slots_arch_lock, which is intentional and desirable despite being
rather unintuitive.
- gmap rewrite: completely new memory management for kvm/s390
- vSIE improvement
- maintainership change for s390 vfio-pci
- small quality of life improvement for protected guests
KVM SVM changes for 6.20
- Drop a user-triggerable WARN on nested_svm_load_cr3() failure.
- Add support for virtualizing ERAPS. Note, correct virtualization of ERAPS
relies on an upcoming, publicly announced change in the APM to reduce the
set of conditions where hardware (i.e. KVM) *must* flush the RAP.
- Ignore nSVM intercepts for instructions that are not supported according to
L1's virtual CPU model.
- Add support for expedited writes to the fast MMIO bus, a la VMX's fastpath
for EPT Misconfig.
- Don't set GIF when clearing EFER.SVME, as GIF exists independently of SVM,
and allow userspace to restore nested state with GIF=0.
- Treat exit_code as an unsigned 64-bit value through all of KVM.
- Add support for fetching SNP certificates from userspace.
- Fix a bug where KVM would use vmcb02 instead of vmcb01 when emulating VMLOAD
or VMSAVE on behalf of L2.
- Misc fixes and cleanups.
The newly added structure causes a warning about implied padding:
./usr/include/linux/kvm.h:1247:1: error: padding struct size to alignment boundary with 6 bytes [-Werror=padded]
The padding can lead to leaking kernel data and ABI incompatibilies
when used on x86. Neither of these is a problem in this specific
patch, but it's best to avoid it and use explicit padding fields
in general.
Fixes: 0ee4ddc164 ("KVM: s390: Storage key manipulation IOCTL")
Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Claudio Imbrenda <[email protected]>
Signed-off-by: Claudio Imbrenda <[email protected]>
Add a new IOCTL to allow userspace to manipulate storage keys directly.
This will make it easier to write selftests related to storage keys.
Acked-by: Heiko Carstens <[email protected]>
Signed-off-by: Claudio Imbrenda <[email protected]>
For SEV-SNP, the host can optionally provide a certificate table to the
guest when it issues an attestation request to firmware (see GHCB 2.0
specification regarding "SNP Extended Guest Requests"). This certificate
table can then be used to verify the endorsement key used by firmware to
sign the attestation report.
While it is possible for guests to obtain the certificates through other
means, handling it via the host provides more flexibility in being able
to keep the certificate data in sync with the endorsement key throughout
host-side operations that might resulting in the endorsement key
changing.
In the case of KVM, userspace will be responsible for fetching the
certificate table and keeping it in sync with any modifications to the
endorsement key by other userspace management tools. Define a new
KVM_EXIT_SNP_REQ_CERTS event where userspace is provided with the GPA of
the buffer the guest has provided as part of the attestation request so
that userspace can write the certificate data into it while relying on
filesystem-based locking to keep the certificates up-to-date relative to
the endorsement keys installed/utilized by firmware at the time the
certificates are fetched.
[Melody: Update the documentation scheme about how file locking is
expected to happen.]
Reviewed-by: Liam Merwick <[email protected]>
Tested-by: Liam Merwick <[email protected]>
Tested-by: Dionna Glaze <[email protected]>
Signed-off-by: Michael Roth <[email protected]>
Signed-off-by: Melody Wang <[email protected]>
Signed-off-by: Michael Roth <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>
The main use of {LD,ST}64B* is to talk to a device, which is hopefully
directly assigned to the guest and requires no additional handling.
However, this does not preclude a VMM from exposing a virtual device
to the guest, and to allow 64 byte accesses as part of the programming
interface. A direct consequence of this is that we need to be able
to forward such access to userspace.
Given that such a contraption is very unlikely to ever exist, we choose
to offer a limited service: userspace gets (as part of a new exit reason)
the ESR, the IPA, and that's it. It is fully expected to handle the full
semantics of the instructions, deal with ACCDATA, the return values and
increment PC. Much fun.
A canonical implementation can also simply inject an abort and be done
with it. Frankly, don't try to do anything else unless you have time
to waste.
Acked-by: Arnd Bergmann <[email protected]>
Acked-by: Oliver Upton <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Signed-off-by: Yicong Yang <[email protected]>
Signed-off-by: Zhou Wang <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
Remove KVM's internal pseudo-overlay of kvm_stats_desc, which subtly
aliases the flexible name[] in the uAPI definition with a fixed-size array
of the same name. The unusual embedded structure results in compiler
warnings due to -Wflex-array-member-not-at-end, and also necessitates an
extra level of dereferencing in KVM. To avoid the "overlay", define the
uAPI structure to have a fixed-size name when building for the kernel.
Opportunistically clean up the indentation for the stats macros, and
replace spaces with tabs.
No functional change intended.
Reported-by: Gustavo A. R. Silva <[email protected]>
Closes: https://lore.kernel.org/all/aPfNKRpLfhmhYqfP@kspp
Acked-by: Marc Zyngier <[email protected]>
Acked-by: Christian Borntraeger <[email protected]>
[..]
Acked-by: Anup Patel <[email protected]>
Reviewed-by: Bibo Mao <[email protected]>
Acked-by: Gustavo A. R. Silva <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>
Setting KVM_CAP_S390_USER_OPEREXEC will forward all operation
exceptions to user space. This also includes the 0x0000 instructions
managed by KVM_CAP_S390_USER_INSTR0. It's helpful if user space wants
to emulate instructions which do not (yet) have an opcode.
While we're at it refine the documentation for
KVM_CAP_S390_USER_INSTR0.
Signed-off-by: Janosch Frank <[email protected]>
Reviewed-by: Claudio Imbrenda <[email protected]>
Acked-by: Christian Borntraeger <[email protected]>
Signed-off-by: Janosch Frank <[email protected]>
When APEI fails to handle a stage-2 synchronous external abort (SEA),
today KVM injects an asynchronous SError to the VCPU then resumes it,
which usually results in unpleasant guest kernel panic.
One major situation of guest SEA is when vCPU consumes recoverable
uncorrected memory error (UER). Although SError and guest kernel panic
effectively stops the propagation of corrupted memory, guest may
re-use the corrupted memory if auto-rebooted; in worse case, guest
boot may run into poisoned memory. So there is room to recover from
an UER in a more graceful manner.
Alternatively KVM can redirect the synchronous SEA event to VMM to
- Reduce blast radius if possible. VMM can inject a SEA to VCPU via
KVM's existing KVM_SET_VCPU_EVENTS API. If the memory poison
consumption or fault is not from guest kernel, blast radius can be
limited to the triggering thread in guest userspace, so VM can
keep running.
- Allow VMM to protect from future memory poison consumption by
unmapping the page from stage-2, or to interrupt guest of the
poisoned page so guest kernel can unmap it from stage-1 page table.
- Allow VMM to track SEA events that VM customers care about, to restart
VM when certain number of distinct poison events have happened,
to provide observability to customers in log management UI.
Introduce an userspace-visible feature to enable VMM handle SEA:
- KVM_CAP_ARM_SEA_TO_USER. As the alternative fallback behavior
when host APEI fails to claim a SEA, userspace can opt in this new
capability to let KVM exit to userspace during SEA if it is not
owned by host.
- KVM_EXIT_ARM_SEA. A new exit reason is introduced for this.
KVM fills kvm_run.arm_sea with as much as possible information about
the SEA, enabling VMM to emulate SEA to guest by itself.
- Sanitized ESR_EL2. The general rule is to keep only the bits
useful for userspace and relevant to guest memory.
- Flags indicating if faulting guest physical address is valid.
- Faulting guest physical and virtual addresses if valid.
Signed-off-by: Jiaqi Yan <[email protected]>
Co-developed-by: Oliver Upton <[email protected]>
Signed-off-by: Oliver Upton <[email protected]>
Link: https://msgid.link/[email protected]
Signed-off-by: Oliver Upton <[email protected]>
Add a guest_memfd flag to allow userspace to state that the underlying
memory should be configured to be initialized as shared, and reject user
page faults if the guest_memfd instance's memory isn't shared. Because
KVM doesn't yet support in-place private<=>shared conversions, all
guest_memfd memory effectively follows the initial state.
Alternatively, KVM could deduce the initial state based on MMAP, which for
all intents and purposes is what KVM currently does. However, implicitly
deriving the default state based on MMAP will result in a messy ABI when
support for in-place conversions is added.
For x86 CoCo VMs, which don't yet support MMAP, memory is currently private
by default (otherwise the memory would be unusable). If MMAP implies
memory is shared by default, then the default state for CoCo VMs will vary
based on MMAP, and from userspace's perspective, will change when in-place
conversion support is added. I.e. to maintain guest<=>host ABI, userspace
would need to immediately convert all memory from shared=>private, which
is both ugly and inefficient. The inefficiency could be avoided by adding
a flag to state that memory is _private_ by default, irrespective of MMAP,
but that would lead to an equally messy and hard to document ABI.
Bite the bullet and immediately add a flag to control the default state so
that the effective behavior is explicit and straightforward.
Fixes: 3d3a04fad2 ("KVM: Allow and advertise support for host mmap() on guest_memfd files")
Cc: David Hildenbrand <[email protected]>
Reviewed-by: Fuad Tabba <[email protected]>
Tested-by: Fuad Tabba <[email protected]>
Reviewed-by: Ackerley Tng <[email protected]>
Tested-by: Ackerley Tng <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>
Rework the not-yet-released KVM_CAP_GUEST_MEMFD_MMAP into a more generic
KVM_CAP_GUEST_MEMFD_FLAGS capability so that adding new flags doesn't
require a new capability, and so that developers aren't tempted to bundle
multiple flags into a single capability.
Note, kvm_vm_ioctl_check_extension_generic() can only return a 32-bit
value, but that limitation can be easily circumvented by adding e.g.
KVM_CAP_GUEST_MEMFD_FLAGS2 in the unlikely event guest_memfd supports more
than 32 flags.
Reviewed-by: Ackerley Tng <[email protected]>
Tested-by: Ackerley Tng <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>
Now that all the x86 and arm64 plumbing for mmap() on guest_memfd is in
place, allow userspace to set GUEST_MEMFD_FLAG_MMAP and advertise support
via a new capability, KVM_CAP_GUEST_MEMFD_MMAP.
The availability of this capability is determined per architecture, and
its enablement for a specific guest_memfd instance is controlled by the
GUEST_MEMFD_FLAG_MMAP flag at creation time.
Update the KVM API documentation to detail the KVM_CAP_GUEST_MEMFD_MMAP
capability, the associated GUEST_MEMFD_FLAG_MMAP, and provide essential
information regarding support for mmap in guest_memfd.
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Gavin Shan <[email protected]>
Reviewed-by: Shivank Garg <[email protected]>
Reviewed-by: Xiaoyao Li <[email protected]>
Signed-off-by: Fuad Tabba <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
Message-ID: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
KVM/arm64 changes for 6.17, round #1
- Host driver for GICv5, the next generation interrupt controller for
arm64, including support for interrupt routing, MSIs, interrupt
translation and wired interrupts.
- Use FEAT_GCIE_LEGACY on GICv5 systems to virtualize GICv3 VMs on
GICv5 hardware, leveraging the legacy VGIC interface.
- Userspace control of the 'nASSGIcap' GICv3 feature, allowing
userspace to disable support for SGIs w/o an active state on hardware
that previously advertised it unconditionally.
- Map supporting endpoints with cacheable memory attributes on systems
with FEAT_S2FWB and DIC where KVM no longer needs to perform cache
maintenance on the address range.
- Nested support for FEAT_RAS and FEAT_DoubleFault2, allowing the guest
hypervisor to inject external aborts into an L2 VM and take traps of
masked external aborts to the hypervisor.
- Convert more system register sanitization to the config-driven
implementation.
- Fixes to the visibility of EL2 registers, namely making VGICv3 system
registers accessible through the VGIC device instead of the ONE_REG
vCPU ioctls.
- Various cleanups and minor fixes.
Allow a guest to read the physical IA32_APERF and IA32_MPERF MSRs
without interception.
The IA32_APERF and IA32_MPERF MSRs are not virtualized. Writes are not
handled at all. The MSR values are not zeroed on vCPU creation, saved
on suspend, or restored on resume. No accommodation is made for
processor migration or for sharing a logical processor with other
tasks. No adjustments are made for non-unit TSC multipliers. The MSRs
do not account for time the same way as the comparable PMU events,
whether the PMU is virtualized by the traditional emulation method or
the new mediated pass-through approach.
Nonetheless, in a properly constrained environment, this capability
can be combined with a guest CPUID table that advertises support for
CPUID.6:ECX.APERFMPERF[bit 0] to induce a Linux guest to report the
effective physical CPU frequency in /proc/cpuinfo. Moreover, there is
no performance cost for this capability.
Signed-off-by: Jim Mattson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Xiaoyao Li <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>
Introduce a new KVM capability to expose to the userspace whether
cacheable mapping of PFNMAP is supported.
The ability to safely do the cacheable mapping of PFNMAP is contingent
on S2FWB and ARM64_HAS_CACHE_DIC. S2FWB allows KVM to avoid flushing
the D cache, ARM64_HAS_CACHE_DIC allows KVM to avoid flushing the icache
and turns icache_inval_pou() into a NOP. The cap would be false if
those requirements are missing and is checked by making use of
kvm_arch_supports_cacheable_pfnmap.
This capability would allow userspace to discover the support.
It could for instance be used by userspace to prevent live-migration
across FWB and non-FWB hosts.
CC: Catalin Marinas <[email protected]>
CC: Jason Gunthorpe <[email protected]>
CC: Oliver Upton <[email protected]>
CC: David Hildenbrand <[email protected]>
Suggested-by: Marc Zyngier <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Tested-by: Donald Dutile <[email protected]>
Signed-off-by: Ankit Agrawal <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Oliver Upton <[email protected]>
Exit to userspace for TDG.VP.VMCALL<GetTdVmCallInfo> via KVM_EXIT_TDX,
to allow userspace to provide information about the support of
TDVMCALLs when r12 is 1 for the TDVMCALLs beyond the GHCI base API.
GHCI spec defines the GHCI base TDVMCALLs: <GetTdVmCallInfo>, <MapGPA>,
<ReportFatalError>, <Instruction.CPUID>, <#VE.RequestMMIO>,
<Instruction.HLT>, <Instruction.IO>, <Instruction.RDMSR> and
<Instruction.WRMSR>. They must be supported by VMM to support TDX guests.
For GetTdVmCallInfo
- When leaf (r12) to enumerate TDVMCALL functionality is set to 0,
successful execution indicates all GHCI base TDVMCALLs listed above are
supported.
Update the KVM TDX document with the set of the GHCI base APIs.
- When leaf (r12) to enumerate TDVMCALL functionality is set to 1, it
indicates the TDX guest is querying the supported TDVMCALLs beyond
the GHCI base TDVMCALLs.
Exit to userspace to let userspace set the TDVMCALL sub-function bit(s)
accordingly to the leaf outputs. KVM could set the TDVMCALL bit(s)
supported by itself when the TDVMCALLs don't need support from userspace
after returning from userspace and before entering guest. Currently, no
such TDVMCALLs implemented, KVM just sets the values returned from
userspace.
Suggested-by: Paolo Bonzini <[email protected]>
Signed-off-by: Binbin Wu <[email protected]>
[Adjust userspace API. - Paolo]
Signed-off-by: Paolo Bonzini <[email protected]>
Handle TDVMCALL for GetQuote to generate a TD-Quote.
GetQuote is a doorbell-like interface used by TDX guests to request VMM
to generate a TD-Quote signed by a service hosting TD-Quoting Enclave
operating on the host. A TDX guest passes a TD Report (TDREPORT_STRUCT) in
a shared-memory area as parameter. Host VMM can access it and queue the
operation for a service hosting TD-Quoting enclave. When completed, the
Quote is returned via the same shared-memory area.
KVM only checks the GPA from the TDX guest has the shared-bit set and drops
the shared-bit before exiting to userspace to avoid bleeding the shared-bit
into KVM's exit ABI. KVM forwards the request to userspace VMM (e.g. QEMU)
and userspace VMM queues the operation asynchronously. KVM sets the return
code according to the 'ret' field set by userspace to notify the TDX guest
whether the request has been queued successfully or not. When the request
has been queued successfully, the TDX guest can poll the status field in
the shared-memory area to check whether the Quote generation is completed
or not. When completed, the generated Quote is returned via the same
buffer.
Add KVM_EXIT_TDX as a new exit reason to userspace. Userspace is
required to handle the KVM exit reason as the initial support for TDX,
by reentering KVM to ensure that the TDVMCALL is complete. While at it,
add a note that KVM_EXIT_HYPERCALL also requires reentry with KVM_RUN.
Signed-off-by: Binbin Wu <[email protected]>
Tested-by: Mikko Ylinen <[email protected]>
Acked-by: Kai Huang <[email protected]>
[Adjust userspace API. - Paolo]
Signed-off-by: Paolo Bonzini <[email protected]>
KVM/riscv changes for 6.16
- Add vector registers to get-reg-list selftest
- VCPU reset related improvements
- Remove scounteren initialization from VCPU reset
- Support VCPU reset from userspace using set_mpstate() ioctl
KVM/arm64 updates for 6.16
* New features:
- Add large stage-2 mapping support for non-protected pKVM guests,
clawing back some performance.
- Add UBSAN support to the standalone EL2 object used in nVHE/hVHE and
protected modes.
- Enable nested virtualisation support on systems that support it
(yes, it has been a long time coming), though it is disabled by
default.
* Improvements, fixes and cleanups:
- Large rework of the way KVM tracks architecture features and links
them with the effects of control bits. This ensures correctness of
emulation (the data is automatically extracted from the published
JSON files), and helps dealing with the evolution of the
architecture.
- Significant changes to the way pKVM tracks ownership of pages,
avoiding page table walks by storing the state in the hypervisor's
vmemmap. This in turn enables the THP support described above.
- New selftest checking the pKVM ownership transition rules
- Fixes for FEAT_MTE_ASYNC being accidentally advertised to guests
even if the host didn't have it.
- Fixes for the address translation emulation, which happened to be
rather buggy in some specific contexts.
- Fixes for the PMU emulation in NV contexts, decoupling PMCR_EL0.N
from the number of counters exposed to a guest and addressing a
number of issues in the process.
- Add a new selftest for the SVE host state being corrupted by a
guest.
- Keep HCR_EL2.xMO set at all times for systems running with the
kernel at EL2, ensuring that the window for interrupts is slightly
bigger, and avoiding a pretty bad erratum on the AmpereOne HW.
- Add workaround for AmpereOne's erratum AC04_CPU_23, which suffers
from a pretty bad case of TLB corruption unless accesses to HCR_EL2
are heavily synchronised.
- Add a per-VM, per-ITS debugfs entry to dump the state of the ITS
tables in a human-friendly fashion.
- and the usual random cleanups.
Add a toggleable VM capability to reset the VCPU from userspace by
setting MP_STATE_INIT_RECEIVED through IOCTL.
Reset through a mp_state to avoid adding a new IOCTL.
Do not reset on a transition from STOPPED to RUNNABLE, because it's
better to avoid side effects that would complicate userspace adoption.
The MP_STATE_INIT_RECEIVED is not a permanent mp_state -- IOCTL resets
the VCPU while preserving the original mp_state -- because we wouldn't
gain much from having a new state it in the rest of KVM, but it's a very
non-standard use of the IOCTL.
Signed-off-by: Radim Krčmář <[email protected]>
Reviewed-by: Anup Patel <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Anup Patel <[email protected]>
Since we're (almost) feature complete, let's allow userspace to
request KVM_ARM_VCPU_EL2* by bumping KVM_VCPU_MAX_FEATURES up.
We also now advertise the features to userspace with new capabilities.
It's going to be great...
Reviewed-by: Oliver Upton <[email protected]>
Reviewed-by: Joey Gouly <[email protected]>
Reviewed-by: Ganapatrao Kulkarni <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Marc Zyngier <[email protected]>
This large commit contains the initial support for TDX in KVM. All x86
parts enable the host-side hypercalls that KVM uses to talk to the TDX
module, a software component that runs in a special CPU mode called SEAM
(Secure Arbitration Mode).
The series is in turn split into multiple sub-series, each with a separate
merge commit:
- Initialization: basic setup for using the TDX module from KVM, plus
ioctls to create TDX VMs and vCPUs.
- MMU: in TDX, private and shared halves of the address space are mapped by
different EPT roots, and the private half is managed by the TDX module.
Using the support that was added to the generic MMU code in 6.14,
add support for TDX's secure page tables to the Intel side of KVM.
Generic KVM code takes care of maintaining a mirror of the secure page
tables so that they can be queried efficiently, and ensuring that changes
are applied to both the mirror and the secure EPT.
- vCPU enter/exit: implement the callbacks that handle the entry of a TDX
vCPU (via the SEAMCALL TDH.VP.ENTER) and the corresponding save/restore
of host state.
- Userspace exits: introduce support for guest TDVMCALLs that KVM forwards to
userspace. These correspond to the usual KVM_EXIT_* "heavyweight vmexits"
but are triggered through a different mechanism, similar to VMGEXIT for
SEV-ES and SEV-SNP.
- Interrupt handling: support for virtual interrupt injection as well as
handling VM-Exits that are caused by vectored events. Exclusive to
TDX are machine-check SMIs, which the kernel already knows how to
handle through the kernel machine check handler (commit 7911f145de,
"x86/mce: Implement recovery for errors in TDX/SEAM non-root mode")
- Loose ends: handling of the remaining exits from the TDX module, including
EPT violation/misconfig and several TDVMCALL leaves that are handled in
the kernel (CPUID, HLT, RDMSR/WRMSR, GetTdVmCallInfo); plus returning
an error or ignoring operations that are not supported by TDX guests
Signed-off-by: Paolo Bonzini <[email protected]>
Convert TDG.VP.VMCALL<ReportFatalError> to KVM_EXIT_SYSTEM_EVENT with
a new type KVM_SYSTEM_EVENT_TDX_FATAL and forward it to userspace for
handling.
TD guest can use TDG.VP.VMCALL<ReportFatalError> to report the fatal
error it has experienced. This hypercall is special because TD guest
is requesting a termination with the error information, KVM needs to
forward the hypercall to userspace anyway, KVM doesn't do parsing or
conversion, it just dumps the 16 general-purpose registers to userspace
and let userspace decide what to do.
Signed-off-by: Binbin Wu <[email protected]>
Message-ID: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
KVM's treatment of the ID registers that describe the implementation
(MIDR, REVIDR, and AIDR) is interesting, to say the least. On the
userspace-facing end of it, KVM presents the values of the boot CPU on
all vCPUs and treats them as invariant. On the guest side of things KVM
presents the hardware values of the local CPU, which can change during
CPU migration in a big-little system.
While one may call this fragile, there is at least some degree of
predictability around it. For example, if a VMM wanted to present
big-little to a guest, it could affine vCPUs accordingly to the correct
clusters.
All of this makes a giant mess out of adding support for making these
implementation ID registers writable. Avoid breaking the rather subtle
ABI around the old way of doing things by requiring opt-in from
userspace to make the registers writable.
When the cap is enabled, allow userspace to set MIDR, REVIDR, and AIDR
to any non-reserved value and present those values consistently across
all vCPUs.
Signed-off-by: Sebastian Ott <[email protected]>
[oliver: changelog, capability]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Oliver Upton <[email protected]>
Drop the KVM_X86_DISABLE_VALID_EXITS definition, as it is misleading, and
unused in KVM *because* it is misleading. The set of exits that can be
disabled is dynamic, i.e. userspace (and KVM) must check KVM's actual
capabilities.
Suggested-by: Xiaoyao Li <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>
Define KVM_REG_SIZE() in the common kvm.h header, and delete the arm64 and
RISC-V versions. As evidenced by the surrounding definitions, all aspects
of the register size encoding are generic, i.e. RISC-V should have moved
arm64's definition to common code instead of copy+pasting.
Acked-by: Anup Patel <[email protected]>
Reviewed-by: Andrew Jones <[email protected]>
Reviewed-by: Muhammad Usama Anjum <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>
KVM x86 misc changes for 6.11
- Add a global struct to consolidate tracking of host values, e.g. EFER, and
move "shadow_phys_bits" into the structure as "maxphyaddr".
- Add KVM_CAP_X86_APIC_BUS_CYCLES_NS to allow configuring the effective APIC
bus frequency, because TDX.
- Print the name of the APICv/AVIC inhibits in the relevant tracepoint.
- Clean up KVM's handling of vendor specific emulation to consistently act on
"compatible with Intel/AMD", versus checking for a specific vendor.
- Misc cleanups
KVM generic changes for 6.11
- Enable halt poll shrinking by default, as Intel found it to be a clear win.
- Setup empty IRQ routing when creating a VM to avoid having to synchronize
SRCU when creating a split IRQCHIP on x86.
- Rework the sched_in/out() paths to replace kvm_arch_sched_in() with a flag
that arch code can use for hooking both sched_in() and sched_out().
- Take the vCPU @id as an "unsigned long" instead of "u32" to avoid
truncating a bogus value from userspace, e.g. to help userspace detect bugs.
- Mark a vCPU as preempted if and only if it's scheduled out while in the
KVM_RUN loop, e.g. to avoid marking it preempted and thus writing guest
memory when retrieving guest state during live migration blackout.
- A few minor cleanups
Ensure that any new KVM code that references immediate_exit gets extra
scrutiny by renaming it to immediate_exit__unsafe in kernel code.
All fields in struct kvm_run are subject to TOCTOU races since they are
mapped into userspace, which may be malicious or buggy. To protect KVM,
introduces a new macro that appends __unsafe to select field names in
struct kvm_run, hinting to developers and reviewers that accessing such
fields must be done carefully.
Apply the new macro to immediate_exit, since userspace can make
immediate_exit inconsistent with vcpu->wants_to_run, i.e. accessing
immediate_exit directly could lead to unexpected bugs in the future.
Signed-off-by: David Matlack <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[sean: massage changelog]
Signed-off-by: Sean Christopherson <[email protected]>
When a vCPU is interrupted by a signal while running a nested guest,
KVM will exit to userspace with L2 state. However, userspace has no
way to know whether it sees L1 or L2 state (besides calling
KVM_GET_STATS_FD, which does not have a stable ABI).
This causes multiple problems:
The simplest one is L2 state corruption when userspace marks the sregs
as dirty. See this mailing list thread [1] for a complete discussion.
Another problem is that if userspace decides to continue by emulating
instructions, it will unknowingly emulate with L2 state as if L1
doesn't exist, which can be considered a weird guest escape.
Introduce a new flag, KVM_RUN_X86_GUEST_MODE, in the kvm_run data
structure, which is set when the vCPU exited while running a nested
guest. Also introduce a new capability, KVM_CAP_X86_GUEST_MODE, to
advertise the functionality to userspace.
[1] https://lore.kernel.org/kvm/[email protected]/T/#m280aadcb2e10ae02c191a7dc4ed4b711a74b1f55
Signed-off-by: Thomas Prescher <[email protected]>
Signed-off-by: Julian Stecklina <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>
Linus Torvalds