linux-kernel - [PATCH v5.4 1/1] iommu/vt-d: Fix agaw for a supported 48 bit guest address width

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Date:   Tue,  6 Apr 2021 09:35:34 -0700
From:   Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     saeed.mirzamohammadi@...cle.com, Camille Lu <camille.lu@....com>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH v5.4 1/1] iommu/vt-d: Fix agaw for a supported 48 bit guest address width

The IOMMU driver calculates the guest addressability for a DMA request
based on the value of the mgaw reported from the IOMMU. However, this
is a fused value and as mentioned in the spec, the guest width
should be calculated based on the supported adjusted guest address width
(SAGAW).

This is from specification:
"Guest addressability for a given DMA request is limited to the
minimum of the value reported through this field and the adjusted
guest address width of the corresponding page-table structure.
(Adjusted guest address widths supported by hardware are reported
through the SAGAW field)."

This causes domain initialization to fail and following
errors appear for EHCI PCI driver:

[    2.486393] ehci-pci 0000:01:00.4: EHCI Host Controller
[    2.486624] ehci-pci 0000:01:00.4: new USB bus registered, assigned bus
number 1
[    2.489127] ehci-pci 0000:01:00.4: DMAR: Allocating domain failed
[    2.489350] ehci-pci 0000:01:00.4: DMAR: 32bit DMA uses non-identity
mapping
[    2.489359] ehci-pci 0000:01:00.4: can't setup: -12
[    2.489531] ehci-pci 0000:01:00.4: USB bus 1 deregistered
[    2.490023] ehci-pci 0000:01:00.4: init 0000:01:00.4 fail, -12
[    2.490358] ehci-pci: probe of 0000:01:00.4 failed with error -12

This issue happens when the value of the sagaw corresponds to a
48-bit agaw. This fix updates the calculation of the agaw based on
the IOMMU's sagaw value.

Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>
Tested-by: Camille Lu <camille.lu@....com>
---
 drivers/iommu/intel-iommu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 953d86ca6d2b..396e14fad54b 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1867,8 +1867,8 @@ static int domain_init(struct dmar_domain *domain, struct intel_iommu *iommu,
 	domain_reserve_special_ranges(domain);

 	/* calculate AGAW */
-	if (guest_width > cap_mgaw(iommu->cap))
-		guest_width = cap_mgaw(iommu->cap);
+	if (guest_width > agaw_to_width(iommu->agaw))
+		guest_width = agaw_to_width(iommu->agaw);
 	domain->gaw = guest_width;
 	adjust_width = guestwidth_to_adjustwidth(guest_width);
 	agaw = width_to_agaw(adjust_width);
-- 
2.27.0