linux-kernel - [PATCH 3/7] iommu/vt-d: Disable PCI ATS in legacy passthrough mode

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Date:   Wed, 22 Nov 2023 11:26:04 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     mohd.syazwan.abdul.halim@...el.com,
        Kunwu Chan <chentao@...inos.cn>, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: [PATCH 3/7] iommu/vt-d: Disable PCI ATS in legacy passthrough mode

When IOMMU hardware operates in legacy mode, the TT field of the context
entry determines the translation type, with three supported types (Section
9.3 Context Entry):

- DMA translation without device TLB support
- DMA translation with device TLB support
- Passthrough mode with translated and translation requests blocked

Device TLB support is absent when hardware is configured in passthrough
mode.

Disable the PCI ATS feature when IOMMU is configured for passthrough
translation type in legacy (non-scalable) mode.

Fixes: 0faa19a1515f ("iommu/vt-d: Decouple PASID & PRI enabling from SVA")
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@...el.com>
Link: https://lore.kernel.org/r/20231114011036.70142-3-baolu.lu@linux.intel.com
---
 drivers/iommu/intel/iommu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 11670cd812a3..9bddd4fbbdf8 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2492,7 +2492,8 @@ static int dmar_domain_attach_device(struct dmar_domain *domain,
 		return ret;
 	}
 
-	iommu_enable_pci_caps(info);
+	if (sm_supported(info->iommu) || !domain_type_is_si(info->domain))
+		iommu_enable_pci_caps(info);
 
 	return 0;
 }
-- 
2.34.1