From: Joe Damato Date: Mon, 9 Mar 2026 23:52:33 +0000 (-0700) Subject: iommu/amd: Block identity domain when SNP enabled X-Git-Tag: v7.0-rc5~24^2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ba17de98545d07285d15ce4fe2afe98283338fb0;p=thirdparty%2Flinux.git iommu/amd: Block identity domain when SNP enabled Previously, commit 8388f7df936b ("iommu/amd: Do not support IOMMU_DOMAIN_IDENTITY after SNP is enabled") prevented users from changing the IOMMU domain to identity if SNP was enabled. This resulted in an error when writing to sysfs: # echo "identity" > /sys/kernel/iommu_groups/50/type -bash: echo: write error: Cannot allocate memory However, commit 4402f2627d30 ("iommu/amd: Implement global identity domain") changed the flow of the code, skipping the SNP guard and allowing users to change the IOMMU domain to identity after a machine has booted. Once the user does that, they will probably try to bind and the device/driver will start to do DMA which will trigger errors: iommu ivhd3: AMD-Vi: Event logged [ILLEGAL_DEV_TABLE_ENTRY device=0000:43:00.0 pasid=0x00000 address=0x3737b01000 flags=0x0020] iommu ivhd3: AMD-Vi: Control Reg : 0xc22000142148d AMD-Vi: DTE[0]: 6000000000000003 AMD-Vi: DTE[1]: 0000000000000001 AMD-Vi: DTE[2]: 2000003088b3e013 AMD-Vi: DTE[3]: 0000000000000000 bnxt_en 0000:43:00.0 (unnamed net_device) (uninitialized): Error (timeout: 500015) msg {0x0 0x0} len:0 iommu ivhd3: AMD-Vi: Event logged [ILLEGAL_DEV_TABLE_ENTRY device=0000:43:00.0 pasid=0x00000 address=0x3737b01000 flags=0x0020] iommu ivhd3: AMD-Vi: Control Reg : 0xc22000142148d AMD-Vi: DTE[0]: 6000000000000003 AMD-Vi: DTE[1]: 0000000000000001 AMD-Vi: DTE[2]: 2000003088b3e013 AMD-Vi: DTE[3]: 0000000000000000 bnxt_en 0000:43:00.0: probe with driver bnxt_en failed with error -16 To prevent this from happening, create an attach wrapper for identity_domain_ops which returns EINVAL if amd_iommu_snp_en is true. With this commit applied: # echo "identity" > /sys/kernel/iommu_groups/62/type -bash: echo: write error: Invalid argument Fixes: 4402f2627d30 ("iommu/amd: Implement global identity domain") Signed-off-by: Joe Damato Reviewed-by: Vasant Hegde Reviewed-by: Jason Gunthorpe Signed-off-by: Joerg Roedel --- diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c index 81c4d7733872..760d5f4623b5 100644 --- a/drivers/iommu/amd/iommu.c +++ b/drivers/iommu/amd/iommu.c @@ -2909,8 +2909,21 @@ static struct iommu_domain blocked_domain = { static struct protection_domain identity_domain; +static int amd_iommu_identity_attach(struct iommu_domain *dom, struct device *dev, + struct iommu_domain *old) +{ + /* + * Don't allow attaching a device to the identity domain if SNP is + * enabled. + */ + if (amd_iommu_snp_en) + return -EINVAL; + + return amd_iommu_attach_device(dom, dev, old); +} + static const struct iommu_domain_ops identity_domain_ops = { - .attach_dev = amd_iommu_attach_device, + .attach_dev = amd_iommu_identity_attach, }; void amd_iommu_init_identity_domain(void)