linux-kernel - Re: [PATCH 2/5] iommu/vt-d: Fix unaligned addresses for intel_flush_svm_range

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Date:   Wed, 6 Jan 2021 09:09:50 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Will Deacon <will@...nel.org>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        Ashok Raj <ashok.raj@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Guo Kaijie <Kaijie.Guo@...el.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] iommu/vt-d: Fix unaligned addresses for
 intel_flush_svm_range_dev()

Hi Will,

Happy New Year!

On 2021/1/6 3:03, Will Deacon wrote:
> On Thu, Dec 31, 2020 at 08:53:20AM +0800, Lu Baolu wrote:
>> The VT-d hardware will ignore those Addr bits which have been masked by
>> the AM field in the PASID-based-IOTLB invalidation descriptor. As the
>> result, if the starting address in the descriptor is not aligned with
>> the address mask, some IOTLB caches might not invalidate. Hence people
>> will see below errors.
>>
>> [ 1093.704661] dmar_fault: 29 callbacks suppressed
>> [ 1093.704664] DMAR: DRHD: handling fault status reg 3
>> [ 1093.712738] DMAR: [DMA Read] Request device [7a:02.0] PASID 2
>>                 fault addr 7f81c968d000 [fault reason 113]
>>                 SM: Present bit in first-level paging entry is clear
>>
>> Fix this by using aligned address for PASID-based-IOTLB invalidation.
>>
>> Fixes: 1c4f88b7f1f92 ("iommu/vt-d: Shared virtual address in scalable mode")
>> Reported-and-tested-by: Guo Kaijie <Kaijie.Guo@...el.com>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> ---
>>   drivers/iommu/intel/svm.c | 22 ++++++++++++++++++++--
>>   1 file changed, 20 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
>> index 69566695d032..b16a4791acfb 100644
>> --- a/drivers/iommu/intel/svm.c
>> +++ b/drivers/iommu/intel/svm.c
>> @@ -118,8 +118,10 @@ void intel_svm_check(struct intel_iommu *iommu)
>>   	iommu->flags |= VTD_FLAG_SVM_CAPABLE;
>>   }
>>   
>> -static void intel_flush_svm_range_dev (struct intel_svm *svm, struct intel_svm_dev *sdev,
>> -				unsigned long address, unsigned long pages, int ih)
>> +static void __flush_svm_range_dev(struct intel_svm *svm,
>> +				  struct intel_svm_dev *sdev,
>> +				  unsigned long address,
>> +				  unsigned long pages, int ih)
>>   {
>>   	struct qi_desc desc;
>>   
>> @@ -170,6 +172,22 @@ static void intel_flush_svm_range_dev (struct intel_svm *svm, struct intel_svm_d
>>   	}
>>   }
>>   
>> +static void intel_flush_svm_range_dev(struct intel_svm *svm,
>> +				      struct intel_svm_dev *sdev,
>> +				      unsigned long address,
>> +				      unsigned long pages, int ih)
>> +{
>> +	unsigned long shift = ilog2(__roundup_pow_of_two(pages));
>> +	unsigned long align = (1ULL << (VTD_PAGE_SHIFT + shift));
>> +	unsigned long start = ALIGN_DOWN(address, align);
>> +	unsigned long end = ALIGN(address + (pages << VTD_PAGE_SHIFT), align);
>> +
>> +	while (start < end) {
>> +		__flush_svm_range_dev(svm, sdev, start, align >> VTD_PAGE_SHIFT, ih);
>> +		start += align;
>> +	}
>> +}
> 
> Given that this only seems to be called from intel_invalidate_range(), which
> has to compute 'pages' only to have it pulled apart again here, perhaps it
> would be cleaner for intel_flush_svm_range() to take something like an
> 'order' argument instead?
> 
> What do you think?

We need to clean up here. It's duplicate with the qi_flush_piotlb()
helper. I have a patch under testing for this. I will post it for review
later.

> 
> Will
> 

Best regards,
baolu