linux-kernel - Re: [PATCH v2] efi/unaccepted: Fix off-by-one when checking for overlapping ranges

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Message-ID: <CAMj1kXE65htEpXSL+h1X-zQ2RH4Oc193rac7=PBYMYJvEUBXNA@mail.gmail.com>
Date:   Tue, 28 Nov 2023 12:50:01 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Michael Roth <michael.roth@....com>, linux-efi@...r.kernel.org,
        x86@...nel.org, linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Nikolay Borisov <nik.borisov@...e.com>, stable@...nel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v2] efi/unaccepted: Fix off-by-one when checking for
 overlapping ranges

On Tue, 28 Nov 2023 at 12:25, Vlastimil Babka <vbabka@...e.cz> wrote:
>
> On 11/8/23 12:21, Ard Biesheuvel wrote:
> > On Fri, 3 Nov 2023 at 16:30, Vlastimil Babka <vbabka@...e.cz> wrote:
> >>
> >> On 11/3/23 16:13, Michael Roth wrote:
> >> > When a task needs to accept memory it will scan the accepting_list
> >> > to see if any ranges already being processed by other tasks overlap
> >> > with its range. Due to an off-by-one in the range comparisons, a task
> >> > might falsely determine that an overlapping range is being accepted,
> >> > leading to an unnecessary delay before it begins processing the range.
> >> >
> >> > Fix the off-by-one in the range comparison to prevent this and slightly
> >> > improve performance.
> >> >
> >> > Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
> >> > Link: https://lore.kernel.org/linux-mm/20231101004523.vseyi5bezgfaht5i@amd.com/T/#me2eceb9906fcae5fe958b3fe88e41f920f8335b6
> >> > Reviewed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> >> > Signed-off-by: Michael Roth <michael.roth@....com>
> >>
> >> More justification for introducing a common ranges_overlap() helper somewhere :)
> >>
> >> Acked-by: Vlastimil Babka <vbabka@...e.cz>
> >>
> >
> > Thanks, I'll take this as a fix.
>
> Ping, can't see it in mainline nor -next?
>

Apologies - queued up now.