Re: [RFC PATCH 2/2] mm: mmu_notifier fix for tlb_end_vma

From: Will Deacon <will.deacon@arm.com>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	torvalds@linux-foundation.org, luto@kernel.org, x86@kernel.org,
	bp@alien8.de, riel@surriel.com, jannh@google.com,
	ascannell@google.com, dave.hansen@intel.com,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	David Miller <davem@davemloft.net>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	linux-arch@vger.kernel.org
Subject: Re: [RFC PATCH 2/2] mm: mmu_notifier fix for tlb_end_vma
Date: Thu, 23 Aug 2018 14:41:05 +0100	[thread overview]
Message-ID: <20180823134104.GD1496@brain-police> (raw)
Message-ID: <20180823134105.dW1hUy4qhA1OWD_DRmdCW_L06W_58Ouosu5e8sh80Tc@z> (raw)
In-Reply-To: <20180823084709.19717-3-npiggin@gmail.com>

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.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>  include/asm-generic/tlb.h | 17 +++++++++++++----
>  mm/memory.c               | 10 ----------
>  2 files changed, 13 insertions(+), 14 deletions(-)

I think we only use the notifiers in the KVM code, which appears to leave
the ->invalidate_range() callback empty, so that at least explains why we
haven't run into problems here.

But the change looks correct to me, so:

Acked-by: Will Deacon <will.deacon@arm.com>

Thanks,

Will