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    SubjectRe: [PATCH 5.4 v2 1/1] iommu/vt-d: Fix agaw for a supported 48 bit guest address width
    Date
    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

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