Messages in this thread | | | Subject | Re: [PATCH v5.4 1/1] iommu/vt-d: Fix agaw for a supported 48 bit guest address width | From | Lu Baolu <> | Date | Wed, 7 Apr 2021 09:43:50 +0800 |
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Hi Saeed,
On 4/7/21 12:35 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 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@oracle.com> > Tested-by: Camille Lu <camille.lu@hpe.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);
The spec requires to use a minimum of MGAW and AGAW, so why not,
cap_width = min_t(int, cap_mgaw(iommu->cap), agaw_to_width(iommu->agaw)); if (guest_width > cap_width) guest_width = cap_width;
Best regards, baolu
> domain->gaw = guest_width; > adjust_width = guestwidth_to_adjustwidth(guest_width); > agaw = width_to_agaw(adjust_width); >
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