linux-kernel - Re: [PATCH v5 0/2] MTE support for KVM guest

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Message-ID: <29a7229d-a1ff-98a5-3007-1addcc85aa04@arm.com>
Date:   Wed, 16 Dec 2020 10:22:52 +0000
From:   Steven Price <steven.price@....com>
To:     Haibo Xu <haibo.xu@...aro.org>
Cc:     Marc Zyngier <maz@...nel.org>, Andrew Jones <drjones@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Juan Quintela <quintela@...hat.com>,
        Richard Henderson <richard.henderson@...aro.org>,
        QEMU Developers <qemu-devel@...gnu.org>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        arm-mail-list <linux-arm-kernel@...ts.infradead.org>,
        kvmarm <kvmarm@...ts.cs.columbia.edu>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>,
        Dave Martin <Dave.Martin@....com>,
        lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 0/2] MTE support for KVM guest

On 16/12/2020 07:31, Haibo Xu wrote:
[...]
> Hi Steve,

Hi Haibo

> I have finished verifying the POC on a FVP setup, and the MTE test case can
> be migrated from one VM to another successfully. Since the test case is very
> simple which just maps one page with MTE enabled and does some memory
> access, so I can't say it's OK for other cases.

That's great progress.

> 
> BTW, I noticed that you have sent out patch set v6 which mentions that mapping
> all the guest memory with PROT_MTE was not feasible. So what's the plan for the
> next step? Will new KVM APIs which can facilitate the tag store and recover be
> available?

I'm currently rebasing on top of the KASAN MTE patch series. My plan for 
now is to switch back to not requiring the VMM to supply PROT_MTE (so 
KVM 'upgrades' the pages as necessary) and I'll add an RFC patch on the 
end of the series to add an KVM API for doing bulk read/write of tags. 
That way the VMM can map guest memory without PROT_MTE (so device 'DMA' 
accesses will be unchecked), and use the new API for migration.

Thanks,

Steve