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

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Date:   Mon, 7 Jun 2021 18:07:14 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Steven Price <steven.price@....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 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

-- 
Catalin