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

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Date:   Mon, 12 Apr 2021 07:49:20 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Saeed Mirzamohammadi <saeed.mirzamohammadi@...cle.com>
Cc:     baolu.lu@...ux.intel.com, Camille Lu <camille.lu@....com>,
        David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5.4 v2 1/1] iommu/vt-d: Fix agaw for a supported 48 bit
 guest address width

I guess you need to ask Greg KH <gregkh@...uxfoundation.org> with this
Cc-ing to stable@...r.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@...ux.intel.com 
>> <mailto:baolu.lu@...ux.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@...cle.com 
>>> <mailto:saeed.mirzamohammadi@...cle.com>>
>>> Tested-by: Camille Lu <camille.lu@....com <mailto:camille.lu@....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@...ux.intel.com 
>> <mailto:baolu.lu@...ux.intel.com>>
>>
>> Best regards,
>> baolu
>