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

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Date:   Fri, 24 Aug 2018 06:24:19 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Will Deacon <will.deacon@....com>
Cc:     Nicholas Piggin <npiggin@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        torvalds@...ux-foundation.org, luto@...nel.org, x86@...nel.org,
        bp@...en8.de, 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, Palmer Dabbelt <palmer@...ive.com>,
        linux-riscv@...ts.infradead.org
Subject: Re: [RFC PATCH 2/2] mm: mmu_notifier fix for tlb_end_vma (build
 failures)

On Fri, Aug 24, 2018 at 02:10:27PM +0100, Will Deacon wrote:
> On Fri, Aug 24, 2018 at 06:07:22AM -0700, Guenter Roeck wrote:
> > 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@...il.com>
> > > Acked-by: Will Deacon <will.deacon@....com>
> > 
> > This patch breaks riscv builds in mainline.
> 
> Looks very similar to the breakage we hit on arm64. diff below should fix
> it.
> 

Unfortunately it doesn't.

In file included from ./arch/riscv/include/asm/pgtable.h:26:0,
                 from ./include/linux/memremap.h:7,
                 from ./include/linux/mm.h:27,
                 from arch/riscv/mm/fault.c:23:
./arch/riscv/include/asm/tlb.h: In function ‘tlb_flush’:
./arch/riscv/include/asm/tlb.h:19:18: error: dereferencing pointer to incomplete type ‘struct mmu_gather’
  flush_tlb_mm(tlb->mm);
                  ^
./arch/riscv/include/asm/tlbflush.h:58:35: note: in definition of macro ‘flush_tlb_mm’
  sbi_remote_sfence_vma(mm_cpumask(mm)->bits, 0, -1)

Note that reverting the offending patch does fix the problem,
so there is no secondary problem lurking around.

Guenter