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iommu/amd: Add SNP page mode 0 support

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Newer AMD IOMMUs supports DTE[Mode]=0 for SNP-enabled system. This is
detected using new feature bit (EFR2[SNP_Page_Mode_0_Sup]). If this
feature is enabled, then IOMMU supports:
  - Passthrough mode (i.e. iommu=pt)
  - amd_iommu=pgtbl_v2: Forcing Linux DMA-API to use IOMMU v2 page table
  - Setting up device for SVA mode in the host.

Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Tested-by: Amandeep Kaur Longia <AmandeepKaur.Longia@amd.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
This commit is contained in:
Vasant Hegde 2026-08-11 05:22:57 +00:00 committed by Joerg Roedel
parent c94252cd5b
commit cb2860ad6c
3 changed files with 35 additions and 15 deletions
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4
drivers/iommu/amd/amd_iommu_types.h
View File

@ -113,6 +113,7 @@
#define FEATURE_SNPAVICSUP_GAM(x) \
(FIELD_GET(FEATURE_SNPAVICSUP, x) == 0x1)
#define FEATURE_HT_RANGE_IGNORE BIT_ULL(11)
#define FEATURE_SNP_PAGE_MODE0_SUP BIT_ULL(13)
#define FEATURE_NUM_INT_REMAP_SUP GENMASK_ULL(9, 8)
#define FEATURE_NUM_INT_REMAP_SUP_2K(x) \
@ -419,6 +420,9 @@ extern bool amd_iommu_dump;
pr_info(format, ## arg); \
} while(0);
/* SNP page mode 0 support */
extern bool amd_iommu_snp_mode0_sup;
/* global flag if IOMMUs cache non-present entries */
extern bool amd_iommu_np_cache;
/* Only true if all IOMMUs support device IOTLBs */

42
drivers/iommu/amd/init.c
View File

@ -180,6 +180,9 @@ bool amd_iommu_hatdis;
bool amd_iommu_snp_en;
EXPORT_SYMBOL(amd_iommu_snp_en);
/* SNP page mode 0 support */
bool amd_iommu_snp_mode0_sup;
LIST_HEAD(amd_iommu_pci_seg_list); /* list of all PCI segments */
LIST_HEAD(amd_iommu_list); /* list of all AMD IOMMUs in the system */
LIST_HEAD(amd_ivhd_dev_flags_list); /* list of all IVHD device entry settings */
@ -3394,18 +3397,28 @@ static __init void iommu_snp_enable(void)
#ifdef CONFIG_KVM_AMD_SEV
if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
return;
/*
* The SNP support requires that IOMMU must be enabled, and is
* configured with V1 page table (DTE[Mode] = 0 is not supported).
*/
if (no_iommu || iommu_default_passthrough()) {
pr_warn("SNP: IOMMU disabled or configured in passthrough mode, SNP cannot be supported.\n");
/* SNP support required IOMMU to be ON */
if (no_iommu) {
pr_warn("SNP: IOMMU disabled, SNP cannot be supported.\n");
goto disable_snp;
}
if (amd_iommu_pgtable != PD_MODE_V1) {
pr_warn("SNP: IOMMU is configured with V2 page table mode, SNP cannot be supported.\n");
goto disable_snp;
amd_iommu_snp_mode0_sup = check_feature2(FEATURE_SNP_PAGE_MODE0_SUP);
/*
* If SNP page mode 0 is not enabled, then SNP support requires that IOMMU
* must be configured with V1 page table (DTE[Mode] != 0).
*/
if (!amd_iommu_snp_mode0_sup) {
if (iommu_default_passthrough()) {
pr_warn("SNP: IOMMU configured in passthrough mode, SNP cannot be supported.\n");
goto disable_snp;
}
if (amd_iommu_pgtable != PD_MODE_V1) {
pr_warn("SNP: IOMMU is configured with V2 page table mode, SNP cannot be supported.\n");
goto disable_snp;
}
}
amd_iommu_snp_en = check_feature(FEATURE_SNP);
@ -3940,12 +3953,15 @@ bool amd_iommu_pasid_supported(void)
amd_iommu_gpt_level != PAGE_MODE_5_LEVEL)
return false;
if (!amd_iommu_gt_ppr_supported())
return false;
/*
* Since DTE[Mode]=0 is prohibited on SNP-enabled system
* (i.e. EFR[SNPSup]=1), IOMMUv2 page table cannot be used without
* setting up IOMMUv1 page table.
* If SNP page mode 0 is not supported, then DTE[Mode]=0 is prohibited
* on SNP-enabled system (i.e. EFR[SNPSup]=1). IOMMUv2 page table
* cannot be used without setting up IOMMUv1 page table.
*/
return amd_iommu_gt_ppr_supported() && !amd_iommu_snp_en;
return (!amd_iommu_snp_en) || (amd_iommu_snp_en && amd_iommu_snp_mode0_sup);
}
struct amd_iommu *get_amd_iommu(unsigned int idx)

4
drivers/iommu/amd/iommu.c
View File

@ -2953,9 +2953,9 @@ static int amd_iommu_identity_attach(struct iommu_domain *dom, struct device *de
{
/*
* Don't allow attaching a device to the identity domain if SNP is
* enabled.
* enabled and SNP Mode0 support is not present.
*/
if (amd_iommu_snp_en)
if (amd_iommu_snp_en && !amd_iommu_snp_mode0_sup)
return -EINVAL;
return amd_iommu_attach_device(dom, dev, old);