linux-kernel - Re: [RFC PATCH 2/2] mm: mmu_notifier fix for tlb_end

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Date:   Thu, 23 Aug 2018 13:46:50 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Nicholas Piggin <npiggin@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        torvalds@...ux-foundation.org, luto@...nel.org, x86@...nel.org,
        bp@...en8.de, will.deacon@....com, riel@...riel.com,
        jannh@...gle.com, ascannell@...gle.com, dave.hansen@...el.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        David Miller <davem@...emloft.net>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-arch@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] mm: mmu_notifier fix for tlb_end_vma

On Thu, Aug 23, 2018 at 06:47:09PM +1000, Nicholas Piggin wrote:
> The generic tlb_end_vma does not call invalidate_range mmu notifier,
> and it resets resets the mmu_gather range, which means the notifier
> won't be called on part of the range in case of an unmap that spans
> multiple vmas.
> 
> ARM64 seems to be the only arch I could see that has notifiers and
> uses the generic tlb_end_vma. I have not actually tested it.

We only care about notifiers for KVM but I think it only makes use of
mmu_notifier_invalidate_range_(start|end) which are not affected by the
range reset in mmu_gather.

Your patch looks ok from an arm64 perspective (it would be good if Will
has a look as well since he was the last to touch this part for arm64).

-- 
Catalin