From: Lu Baolu Date: Fri, 26 Sep 2025 02:41:30 +0000 (+0800) Subject: iommu/vt-d: Disallow dirty tracking if incoherent page walk X-Git-Tag: v6.18-rc1~105^2^5 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=57f55048e564dedd8a4546d018e29d6bbfff0a7e;p=thirdparty%2Flinux.git iommu/vt-d: Disallow dirty tracking if incoherent page walk Dirty page tracking relies on the IOMMU atomically updating the dirty bit in the paging-structure entry. For this operation to succeed, the paging- structure memory must be coherent between the IOMMU and the CPU. In another word, if the iommu page walk is incoherent, dirty page tracking doesn't work. The Intel VT-d specification, Section 3.10 "Snoop Behavior" states: "Remapping hardware encountering the need to atomically update A/EA/D bits in a paging-structure entry that is not snooped will result in a non- recoverable fault." To prevent an IOMMU from being incorrectly configured for dirty page tracking when it is operating in an incoherent mode, mark SSADS as supported only when both ecap_slads and ecap_smpwc are supported. Fixes: f35f22cc760e ("iommu/vt-d: Access/Dirty bit support for SS domains") Signed-off-by: Lu Baolu Reviewed-by: Jason Gunthorpe Link: https://lore.kernel.org/r/20250924083447.123224-1-baolu.lu@linux.intel.com Signed-off-by: Joerg Roedel --- diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h index ef7a1ae8e0db..3056583d7f56 100644 --- a/drivers/iommu/intel/iommu.h +++ b/drivers/iommu/intel/iommu.h @@ -537,7 +537,8 @@ enum { #define pasid_supported(iommu) (sm_supported(iommu) && \ ecap_pasid((iommu)->ecap)) #define ssads_supported(iommu) (sm_supported(iommu) && \ - ecap_slads((iommu)->ecap)) + ecap_slads((iommu)->ecap) && \ + ecap_smpwc(iommu->ecap)) #define nested_supported(iommu) (sm_supported(iommu) && \ ecap_nest((iommu)->ecap))