linux-kernel - Re: [PATCH v2 2/3] x86/mm: Make flush_tlb_mm

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Message-ID: <56bf2b62-ecae-65ab-0ade-3c659bfd640c@intel.com>
Date:   Fri, 21 Apr 2017 11:54:06 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Andy Lutomirski <luto@...nel.org>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        Rik van Riel <riel@...hat.com>,
        Nadav Amit <namit@...are.com>, Michal Hocko <mhocko@...e.com>,
        Sasha Levin <sasha.levin@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 2/3] x86/mm: Make flush_tlb_mm_range() more predictable

On 04/21/2017 11:15 AM, Andy Lutomirski wrote:
> I'm about to rewrite the function almost completely, but first I
> want to get a functional change out of the way.  Currently, if
> flush_tlb_mm_range() does not flush the local TLB at all, it will
> never do individual page flushes on remote CPUs.  This seems to be
> an accident, and preserving it will be awkward.  Let's change it
> first so that any regressions in the rewrite will be easier to
> bisect and so that the rewrite can attempt to change no visible
> behavior at all.
> 
> The fix is simple: we can simply avoid short-circuiting the
> calculation of base_pages_to_flush.

This looks sane to me.  I think it makes things more straightforward.

Acked-by: Dave Hansen <dave.hansen@...el.com>