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

[Saeed Mirzamohammadi]

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@xxxxxxxxxxxxxxx> wrote:
> 
> I guess you need to ask Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> with this
> Cc-ing to stable@xxxxxxxxxxxxxxx.
> 
> 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@xxxxxxxxxxxxxxx <mailto:baolu.lu@xxxxxxxxxxxxxxx>> 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@xxxxxxxxxx <mailto:saeed.mirzamohammadi@xxxxxxxxxx>>
>>>> Tested-by: Camille Lu <camille.lu@xxxxxxx <mailto:camille.lu@xxxxxxx>>
>>>> ---
>>>> 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@xxxxxxxxxxxxxxx <mailto:baolu.lu@xxxxxxxxxxxxxxx>>
>>> 
>>> Best regards,
>>> baolu