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

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Message-ID: <b77efceaec433dd98fdf2cd535a9cf40@kernel.org>
Date:   Tue, 08 Dec 2020 10:01:38 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Haibo Xu <haibo.xu@...aro.org>
Cc:     Steven Price <steven.price@....com>,
        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 2020-12-08 09:51, Haibo Xu wrote:
> On Mon, 7 Dec 2020 at 22:48, Steven Price <steven.price@....com> wrote:
>> 

[...]

>> Sounds like you are making good progress - thanks for the update. Have
>> you thought about how the PROT_MTE mappings might work if QEMU itself
>> were to use MTE? My worry is that we end up with MTE in a guest
>> preventing QEMU from using MTE itself (because of the PROT_MTE
>> mappings). I'm hoping QEMU can wrap its use of guest memory in a
>> sequence which disables tag checking (something similar will be needed
>> for the "protected VM" use case anyway), but this isn't something I've
>> looked into.
> 
> As far as I can see, to map all the guest memory with PROT_MTE in VMM
> is a little weird, and lots of APIs have to be changed to include this 
> flag.
> IMHO, it would be better if the KVM can provide new APIs to load/store 
> the
> guest memory tag which may make it easier to enable the Qemu migration
> support.

On what granularity? To what storage? How do you plan to synchronise 
this
with the dirty-log interface?

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...