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KVM: pfncache: Precisely track refcounted pages

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Track refcounted struct page memory using kvm_follow_pfn.refcounted_page
instead of relying on kvm_release_pfn_clean() to correctly detect that the
pfn is associated with a struct page.

Tested-by: Alex Bennée <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
Tested-by: Dmitry Osipenko <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
Message-ID: <[email protected]>
This commit is contained in:
Sean Christopherson authored and Paolo Bonzini committed 2024-10-25 12:57:59 -04:00
1 parent 775e3ff7bf
commit 3154ddcb6a
1 file changed
+7 -4
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virt/kvm/pfncache.c
+7 -4
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@@ -159,11 +159,14 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
kvm_pfn_t new_pfn = KVM_PFN_ERR_FAULT;
void *new_khva = NULL;
unsigned long mmu_seq;
struct page *page;
struct kvm_follow_pfn kfp = {
.slot = gpc->memslot,
.gfn = gpa_to_gfn(gpc->gpa),
.flags = FOLL_WRITE,
.hva = gpc->uhva,
.refcounted_page = &page,
};
lockdep_assert_held(&gpc->refresh_lock);
@@ -198,7 +201,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
if (new_khva != old_khva)
gpc_unmap(new_pfn, new_khva);
kvm_release_pfn_clean(new_pfn);
kvm_release_page_unused(page);
cond_resched();
}
@@ -218,7 +221,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
new_khva = gpc_map(new_pfn);
if (!new_khva) {
kvm_release_pfn_clean(new_pfn);
kvm_release_page_unused(page);
goto out_error;
}
@@ -236,11 +239,11 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
gpc->khva = new_khva + offset_in_page(gpc->uhva);
/*
* Put the reference to the _new_ pfn. The pfn is now tracked by the
* Put the reference to the _new_ page. The page is now tracked by the
* cache and can be safely migrated, swapped, etc... as the cache will
* invalidate any mappings in response to relevant mmu_notifier events.
*/
kvm_release_pfn_clean(new_pfn);
kvm_release_page_clean(page);
return 0;