6.6-stable review patch. If anyone has any objections, please let me know.
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From: Lu Baolu baolu.lu@linux.intel.com
commit 5ef7e24c742038a5d8c626fdc0e3a21834358341 upstream.
The specification, Section 7.10, "Software Steps to Drain Page Requests & Responses," requires software to submit an Invalidation Wait Descriptor (inv_wait_dsc) with the Page-request Drain (PD=1) flag set, along with the Invalidation Wait Completion Status Write flag (SW=1). It then waits for the Invalidation Wait Descriptor's completion.
However, the PD field in the Invalidation Wait Descriptor is optional, as stated in Section 6.5.2.9, "Invalidation Wait Descriptor":
"Page-request Drain (PD): Remapping hardware implementations reporting Page-request draining as not supported (PDS = 0 in ECAP_REG) treat this field as reserved."
This implies that if the IOMMU doesn't support the PDS capability, software can't drain page requests and group responses as expected.
Do not enable PCI/PRI if the IOMMU doesn't support PDS.
Reported-by: Joel Granados joel.granados@kernel.org Closes: https://lore.kernel.org/r/20250909-jag-pds-v1-1-ad8cba0e494e@kernel.org Fixes: 66ac4db36f4c ("iommu/vt-d: Add page request draining support") Cc: stable@vger.kernel.org Signed-off-by: Lu Baolu baolu.lu@linux.intel.com Link: https://lore.kernel.org/r/20250915062946.120196-1-baolu.lu@linux.intel.com Signed-off-by: Joerg Roedel joerg.roedel@amd.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/iommu/intel/iommu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -4415,7 +4415,7 @@ static struct iommu_device *intel_iommu_ }
if (info->ats_supported && ecap_prs(iommu->ecap) && - pci_pri_supported(pdev)) + ecap_pds(iommu->ecap) && pci_pri_supported(pdev)) info->pri_supported = 1; } }