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

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Message-ID: <20231103151531.7e374teoxeekcrlm@amd.com>
Date:   Fri, 3 Nov 2023 10:15:31 -0500
From:   Michael Roth <michael.roth@....com>
To:     "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.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 05:53:53PM +0300, Kirill A . Shutemov wrote:
> 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>

Thanks! Sending a v2 with suggested changes.

-Mike

> > 
> 
> -- 
>   Kiryl Shutsemau / Kirill A. Shutemov