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

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Message-ID: <20231103145353.5wzcwc5znkzt6vzf@box>
Date:   Fri, 3 Nov 2023 17:53:53 +0300
From:   "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Michael Roth <michael.roth@....com>
Cc:     linux-efi@...r.kernel.org, x86@...nel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Nikolay Borisov <nik.borisov@...e.com>, stable@...nel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH] efi/unaccepted: Fix off-by-one when checking for
 overlapping ranges

On Fri, Nov 03, 2023 at 09:26:50AM -0500, Michael Roth wrote:
> When a thread needs to accept memory it will scan the accepting_list
> to see if any ranges already being processed by other threads overlap
> with its range. Due to an off-by-one in the range comparisons, a thread
> might falsely determine that an overlapping range is being accepted,
> leading to an unnecessary delay before it begins processing the range.

Maybe s/thread/task/g ?

> 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
> Signed-off-by: Michael Roth <michael.roth@....com>

Otherwise, looks good:

Reviewed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> 

-- 
  Kiryl Shutsemau / Kirill A. Shutemov