linux-kernel - [PATCH kernel v2 3/5] iommu/amd: Report SEV-TIO support

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Message-ID: <20251121080629.444992-4-aik@amd.com>
Date: Fri, 21 Nov 2025 19:06:27 +1100
From: Alexey Kardashevskiy <aik@....com>
To: <linux-kernel@...r.kernel.org>
CC: <linux-crypto@...r.kernel.org>, Tom Lendacky <thomas.lendacky@....com>,
	John Allen <john.allen@....com>, Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>, Ashish Kalra <ashish.kalra@....com>,
	Joerg Roedel <joro@...tes.org>, Suravee Suthikulpanit
	<suravee.suthikulpanit@....com>, Will Deacon <will@...nel.org>, Robin Murphy
	<robin.murphy@....com>, "Borislav Petkov (AMD)" <bp@...en8.de>, Kim Phillips
	<kim.phillips@....com>, Jerry Snitselaar <jsnitsel@...hat.com>, Vasant Hegde
	<vasant.hegde@....com>, Jason Gunthorpe <jgg@...pe.ca>, Gao Shiyuan
	<gaoshiyuan@...du.com>, Sean Christopherson <seanjc@...gle.com>, "Nikunj A
 Dadhania" <nikunj@....com>, Michael Roth <michael.roth@....com>, Amit Shah
	<amit.shah@....com>, Peter Gonda <pgonda@...gle.com>,
	<iommu@...ts.linux.dev>, Alexey Kardashevskiy <aik@....com>
Subject: [PATCH kernel v2 3/5] 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 <aik@....com>
---
 drivers/iommu/amd/amd_iommu_types.h | 1 +
 include/linux/amd-iommu.h           | 2 ++
 drivers/iommu/amd/init.c            | 9 +++++++++
 3 files changed, 12 insertions(+)

diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index a698a2e7ce2a..a2f72c53d3cc 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/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)
diff --git a/include/linux/amd-iommu.h b/include/linux/amd-iommu.h
index 8cced632ecd0..0f64f09d1f34 100644
--- a/include/linux/amd-iommu.h
+++ b/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 */
 
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index f2991c11867c..ba95467ba492 100644
--- a/drivers/iommu/amd/init.c
+++ b/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
-- 
2.51.1