linux-kernel - Re: [GIT PULL] KVM changes for 3.12

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Message-ID: <CA+55aFwYvhLS8onJphR0PnL5e0zyS1ki65O_fSC05TeVSw0hDg@mail.gmail.com>
Date:	Wed, 4 Sep 2013 18:08:08 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [GIT PULL] KVM changes for 3.12

On Tue, Sep 3, 2013 at 5:10 AM, Gleb Natapov <gleb@...hat.com> wrote:
>
> This pull request adds tlb_gather_mmu() caller in S390 code, but 2b047252
> in your tree added another parameter to the function, so the patch bellow
> have to be applied during merge to resolve the conflicts. The patch was
> used in linux-next for awhile.

Hmm. Fine. Except:

>         /* Reallocate the page tables with pgstes */
>         mm->context.has_pgste = 1;
> -       tlb_gather_mmu(&tlb, mm, 0);
> +       tlb_gather_mmu(&tlb, mm, 0, TASK_SIZE);
>         page_table_realloc(&tlb, mm, 0, TASK_SIZE);
>         tlb_finish_mmu(&tlb, 0, -1);
>         up_write(&mm->mmap_sem);

Realistically, the begin/end arguments to tlb_gather_mmu() and
tlb_finish_mmu() should match. In fact, I considered getting rid of
the ones to tlb_finish_mmu() because they are kind of pointless these
days (but didn't, because I wanted to keep the patches minimal).

And in your case they don't. Which implies a certain amount of confusion.

It looks like it's not really a full-mm invalidate (it's not the final
TLB flush before getting rid of the VM), so I think "0, TASK_SIZE" is
correct. I just think I'm going to also change that tlb_finish_mmu()
to have the same "0, TASK_SIZE" range, so that it's all consistent.

It appears that s390 doesn't actually care about the range to
tlb_finish_mmu(), so this is pretty academic, but I thought I'd
mention it so that it doesn't come as a surprise that my merge
resolution looks different from your suggested one.

              Linus
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