iommu/amd: Report SEV-TIO support

The SEV-TIO switch in the AMD BIOS is reported to the OS via
the IOMMU Extended Feature 2 register (EFR2), bit 1.

Add helper to parse the bit and report the feature presence.

Signed-off-by: Alexey Kardashevskiy <[email protected]>
Link: https://patch.msgid.link/[email protected]
Acked-by: Joerg Roedel <[email protected]>
Reviewed-by: Vasant Hegde <[email protected]>
Acked-by: Tom Lendacky <[email protected]>
Signed-off-by: Dan Williams <[email protected]>

drivers/iommu/amd/amd_iommu_types.h

@@ -107,6 +107,7 @@
 
 
 /* Extended Feature 2 Bits */
+#define FEATURE_SEVSNPIO_SUP	BIT_ULL(1)
 #define FEATURE_SNPAVICSUP	GENMASK_ULL(7, 5)
 #define FEATURE_SNPAVICSUP_GAM(x) \
 	(FIELD_GET(FEATURE_SNPAVICSUP, x) == 0x1)

drivers/iommu/amd/init.c

@@ -2252,6 +2252,9 @@ static void print_iommu_info(void)
 		if (check_feature(FEATURE_SNP))
 			pr_cont(" SNP");
 
+		if (check_feature2(FEATURE_SEVSNPIO_SUP))
+			pr_cont(" SEV-TIO");
+
 		pr_cont("\n");
 	}
 
@@ -4015,4 +4018,10 @@ int amd_iommu_snp_disable(void)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(amd_iommu_snp_disable);
+
+bool amd_iommu_sev_tio_supported(void)
+{
+	return check_feature2(FEATURE_SEVSNPIO_SUP);
+}
+EXPORT_SYMBOL_GPL(amd_iommu_sev_tio_supported);
 #endif

include/linux/amd-iommu.h

@@ -18,10 +18,12 @@ struct task_struct;
 struct pci_dev;
 
 extern void amd_iommu_detect(void);
+extern bool amd_iommu_sev_tio_supported(void);
 
 #else /* CONFIG_AMD_IOMMU */
 
 static inline void amd_iommu_detect(void) { }
+static inline bool amd_iommu_sev_tio_supported(void) { return false; }
 
 #endif /* CONFIG_AMD_IOMMU */