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

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Date:   Fri, 8 Jan 2021 22:30:14 +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,

On 2021/1/8 22:09, Will Deacon wrote:
> Hi Lu,
> 
> On Fri, Jan 08, 2021 at 07:52:47AM +0800, Lu Baolu wrote:
>> On 2021/1/6 9:09, Lu Baolu wrote:
>>> On 2021/1/6 3:03, Will Deacon wrote:
>>>> On Thu, Dec 31, 2020 at 08:53:20AM +0800, Lu Baolu wrote:
>>>>> @@ -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.
>>
>> I'm sorry, above reply is a little vague.
>>
>> I meant to say, let's take 'pages' as the argument. We are going to use
>> qi_flush_piotlb() here to avoid duplicate QI interactions. The
>> qi_flush_piotlb() helper also takes 'pages', so keep 'pages' here will
>> make things easier.
>>
>> My cleanup patch is for v5.12. Can you please take this for v5.11?
> 
> Ah sorry, I didn't realise that was your plan. Please just include this
> patch in a series of 2 when you post a fixed version of the trace event
> removal and then I'll queue them up next week, as I've already prepared
> the pull for today.

Sure and sorry for my vague reply.

> 
> Apologies,

It's okay. :-)

> 
> Will
> 

Best regards,
baolu