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 14:09:32 +0000
From:   Will Deacon <will@...nel.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     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 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.

Apologies,

Will