linux-kernel - [PATCH v2 2/2] iommu/vt-d: Enable ATS only if the device uses page aligned address.

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Message-Id: <457841852e067af6f02297b0d0bccbf66ed308b6.1549920354.git.sathyanarayanan.kuppuswamy@linux.intel.com>
Date:   Mon, 11 Feb 2019 13:44:35 -0800
From:   sathyanarayanan.kuppuswamy@...ux.intel.com
To:     bhelgaas@...gle.com, joro@...tes.org, dwmw2@...radead.org
Cc:     linux-pci@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, ashok.raj@...el.com,
        jacob.jun.pan@...el.com, keith.busch@...el.com,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Subject: [PATCH v2 2/2] iommu/vt-d: Enable ATS only if the device uses page aligned address.

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>

As per Intel vt-d specification, Rev 3.0 (section 7.5.1.1, title "Page
Request Descriptor"), Intel IOMMU page request descriptor only uses
bits[63:12] of the page address. Hence Intel IOMMU driver would only
permit devices that advertise they would only send page aligned requests
to participate in ATS service.

Cc: Ashok Raj <ashok.raj@...el.com>
Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc: Keith Busch <keith.busch@...el.com>
Suggested-by: Ashok Raj <ashok.raj@...el.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
---
 drivers/iommu/intel-iommu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 1457f931218e..6a0b5270cd2e 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1406,6 +1406,7 @@ static void iommu_enable_dev_iotlb(struct device_domain_info *info)
 		info->pri_enabled = 1;
 #endif
 	if (!pdev->untrusted && info->ats_supported &&
+	    pci_ats_page_aligned(pdev) &&
 	    !pci_enable_ats(pdev, VTD_PAGE_SHIFT)) {
 		info->ats_enabled = 1;
 		domain_update_iotlb(info->domain);
-- 
2.20.1