Messages in this thread Patch in this message | | | From | Suravee Suthikulpanit <> | Subject | [PATCH v3 6/7] iommu/amd: Do not support IOMMU_DOMAIN_IDENTITY after SNP is enabled | Date | Wed, 22 Jun 2022 12:11:30 -0500 |
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Once SNP is enabled (by executing SNP_INIT command), IOMMU can no longer support the passthrough domain (i.e. IOMMU_DOMAIN_IDENTITY).
The SNP_INIT command is called early in the boot process, and would fail if the kernel is configure to default to passthrough mode.
After the system is already booted, users can try to change IOMMU domain type of a particular IOMMU group. In this case, the IOMMU driver needs to check the SNP-enable status and return failure when requesting to change domain type to identity.
Therefore, return failure when trying to allocate identity domain.
Reviewed-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com> --- drivers/iommu/amd/iommu.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c index 4f4571d3ff61..7093e26fec59 100644 --- a/drivers/iommu/amd/iommu.c +++ b/drivers/iommu/amd/iommu.c @@ -2119,6 +2119,14 @@ static struct iommu_domain *amd_iommu_domain_alloc(unsigned type) { struct protection_domain *domain; + /* + * Since DTE[Mode]=0 is prohibited on SNP-enabled system, + * default to use IOMMU_DOMAIN_DMA[_FQ]. + */ + if (WARN_ONCE(amd_iommu_snp_en && (type == IOMMU_DOMAIN_IDENTITY), + "Cannot allocate identity domain due to SNP\n")) + return NULL; + domain = protection_domain_alloc(type); if (!domain) return NULL; -- 2.32.0
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