linux-kernel - Re: [PATCH v14 2/8] arm64: Handle MTE tags zeroing in __alloc_zeroed_user

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Message-ID: <7a3f14de-211b-94f9-6886-393d233193d5@arm.com>
Date:   Wed, 9 Jun 2021 09:56:43 +0100
From:   Steven Price <steven.price@....com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Dave Martin <Dave.Martin@....com>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>, qemu-devel@...gnu.org,
        Juan Quintela <quintela@...hat.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        Richard Henderson <richard.henderson@...aro.org>,
        Peter Maydell <peter.maydell@...aro.org>,
        Haibo Xu <Haibo.Xu@....com>, Andrew Jones <drjones@...hat.com>
Subject: Re: [PATCH v14 2/8] arm64: Handle MTE tags zeroing in
 __alloc_zeroed_user_highpage()

On 07/06/2021 18:07, Catalin Marinas wrote:
> On Mon, Jun 07, 2021 at 12:08:10PM +0100, Steven Price wrote:
>> From: Catalin Marinas <catalin.marinas@....com>
>>
>> Currently, on an anonymous page fault, the kernel allocates a zeroed
>> page and maps it in user space. If the mapping is tagged (PROT_MTE),
>> set_pte_at() additionally clears the tags under a spinlock to avoid a
>> race on the page->flags. In order to optimise the lock, clear the page
>> tags on allocation in __alloc_zeroed_user_highpage() if the vma flags
>> have VM_MTE set.
>>
>> Signed-off-by: Catalin Marinas <catalin.marinas@....com>
>> Signed-off-by: Steven Price <steven.price@....com>
> 
> I think you can drop this patch now that Peter's series has been queued
> via the arm64 tree:
> 
> https://lore.kernel.org/r/20210602235230.3928842-4-pcc@google.com
> 

Thanks for the heads up - I hadn't seen that land. I'll drop this patch
from the next posting.

Steve