Hi Greg,

This patch fixes an issue with the IOMMU driver and it only applies to 5.4, 4.19, and 4.14 stable kernels. May I know when this patch would be available in the stable kernels?

Subject: iommu/vt-d: Fix agaw for a supported 48 bit guest address width

Thanks, Saeed

On Apr 11, 2021, at 4:49 PM, Lu Baolu baolu.lu@linux.intel.com wrote:

I guess you need to ask Greg KH gregkh@linuxfoundation.org with this Cc-ing to stable@vger.kernel.org.

Best regards, baolu

On 2021/4/12 3:36, Saeed Mirzamohammadi wrote:

...

Hi Lu, Thanks for the review. May I know when do we expect this to be applied to 5.4? Thanks, Saeed

...

On Apr 7, 2021, at 5:25 PM, Lu Baolu <baolu.lu@linux.intel.com mailto:baolu.lu@linux.intel.com> wrote:

On 4/8/21 2:40 AM, Saeed Mirzamohammadi wrote:

...

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 minimum of supported adjusted guest address width (SAGAW) and MGAW. 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 minimum of IOMMU's sagaw value and MGAW. Signed-off-by: Saeed Mirzamohammadi <saeed.mirzamohammadi@oracle.com mailto:saeed.mirzamohammadi@oracle.com> Tested-by: Camille Lu <camille.lu@hpe.com mailto:camille.lu@hpe.com>

---

Change in v2:

• Added cap_width to calculate AGAW based on the minimum value of MGAW and AGAW.

---

drivers/iommu/intel-iommu.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c index 953d86ca6d2b..a2a03df97704 100644 --- a/drivers/iommu/intel-iommu.c +++ b/drivers/iommu/intel-iommu.c @@ -1853,7 +1853,7 @@ static inline int guestwidth_to_adjustwidth(int gaw) static int domain_init(struct dmar_domain *domain, struct intel_iommu *iommu, int guest_width) { -int adjust_width, agaw; +int adjust_width, agaw, cap_width; unsigned long sagaw; int err; @@ -1867,8 +1867,9 @@ 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); +cap_width = min_t(int, cap_mgaw(iommu->cap), agaw_to_width(iommu->agaw)); +if (guest_width > cap_width) +guest_width = cap_width; domain->gaw = guest_width; adjust_width = guestwidth_to_adjustwidth(guest_width); agaw = width_to_agaw(adjust_width);

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com mailto:baolu.lu@linux.intel.com>

Best regards, baolu