From: Marc Zyngier <maz@kernel•org>
To: Catalin Marinas <catalin.marinas@arm•com>
Cc: Peter Maydell <peter.maydell@linaro•org>,
Juan Quintela <quintela@redhat•com>,
QEMU Developers <qemu-devel@nongnu•org>,
Dave Martin <Dave.Martin@arm•com>,
Richard Henderson <richard.henderson@linaro•org>,
lkml - Kernel Mailing List <linux-kernel@vger•kernel.org>,
Steven Price <steven.price@arm•com>,
arm-mail-list <linux-arm-kernel@lists•infradead.org>,
Haibo Xu <haibo.xu@linaro•org>,
Thomas Gleixner <tglx@linutronix•de>,
Will Deacon <will@kernel•org>,
kvmarm <kvmarm@lists•cs.columbia.edu>,
"Dr. David Alan Gilbert" <dgilbert@redhat•com>
Subject: Re: [PATCH v5 0/2] MTE support for KVM guest
Date: Wed, 09 Dec 2020 13:25:18 +0000 [thread overview]
Message-ID: <ef14a5158fc65c00f6c3c842cfa83b2c@kernel.org> (raw)
In-Reply-To: <20201209124443.GB13566@gaia>
On 2020-12-09 12:44, Catalin Marinas wrote:
> On Tue, Dec 08, 2020 at 06:21:12PM +0000, Marc Zyngier wrote:
>> On 2020-12-08 17:21, Catalin Marinas wrote:
>> > On Mon, Dec 07, 2020 at 07:03:13PM +0000, Marc Zyngier wrote:
>> > > I wonder whether we will have to have something kernel side to
>> > > dump/reload tags in a way that matches the patterns used by live
>> > > migration.
>> >
>> > We have something related - ptrace dumps/resores the tags. Can the same
>> > concept be expanded to a KVM ioctl?
>>
>> Yes, although I wonder whether we should integrate this deeply into
>> the dirty-log mechanism: it would be really interesting to dump the
>> tags at the point where the page is flagged as clean from a dirty-log
>> point of view. As the page is dirtied, discard the saved tags.
>
> From the VMM perspective, the tags can be treated just like additional
> (meta)data in a page. We'd only need the tags when copying over. It can
> race with the VM dirtying the page (writing tags would dirty it) but I
> don't think the current migration code cares about this. If dirtied, it
> copies it again.
>
> The only downside I see is an extra syscall per page both on the origin
> VMM and the destination one to dump/restore the tags. Is this a
> performance issue?
I'm not sure. Migrating VMs already has a massive overhead, so an extra
syscall per page isn't terrifying. But that's the point where I admit
not knowing enough about what the VMM expects, nor whether that matches
what happens on other architectures that deal with per-page metadata.
Would this syscall operate on the guest address space? Or on the VMM's
own mapping?
M.
--
Jazz is not dead. It just smells funny...
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next prev parent reply other threads:[~2020-12-09 13:26 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-19 15:38 [PATCH v5 0/2] MTE support for KVM guest Steven Price
2020-11-19 15:39 ` [PATCH v5 1/2] arm64: kvm: Save/restore MTE registers Steven Price
2020-11-19 15:39 ` [PATCH v5 2/2] arm64: kvm: Introduce MTE VCPU feature Steven Price
2020-11-19 15:45 ` [PATCH v5 0/2] MTE support for KVM guest Peter Maydell
2020-11-19 15:57 ` Steven Price
2020-11-19 16:39 ` Peter Maydell
2020-11-19 18:42 ` Andrew Jones
2020-11-19 19:11 ` Marc Zyngier
2020-11-20 9:50 ` Steven Price
2020-11-20 9:56 ` Marc Zyngier
2020-11-20 9:58 ` Steven Price
2020-12-04 8:25 ` Haibo Xu
2020-12-07 14:48 ` Steven Price
2020-12-07 15:27 ` Peter Maydell
2020-12-07 15:45 ` Steven Price
2020-12-07 16:05 ` Marc Zyngier
2020-12-07 16:34 ` Catalin Marinas
2020-12-07 19:03 ` Marc Zyngier
2020-12-08 17:21 ` Catalin Marinas
2020-12-08 18:21 ` Marc Zyngier
2020-12-09 12:44 ` Catalin Marinas
2020-12-09 13:25 ` Marc Zyngier [this message]
2020-12-09 15:27 ` Catalin Marinas
2020-12-09 18:27 ` Richard Henderson
2020-12-09 18:39 ` Catalin Marinas
2020-12-09 20:13 ` Richard Henderson
2020-12-09 20:20 ` Peter Maydell
2020-12-07 16:44 ` Dr. David Alan Gilbert
2020-12-07 17:10 ` Peter Maydell
2020-12-07 17:44 ` Dr. David Alan Gilbert
2020-12-08 10:05 ` Haibo Xu
2020-12-08 9:51 ` Haibo Xu
2020-12-08 10:01 ` Marc Zyngier
2020-12-08 10:10 ` Haibo Xu
2020-12-16 7:31 ` Haibo Xu
2020-12-16 10:22 ` Steven Price
2020-12-17 1:47 ` Haibo Xu
2020-11-23 12:16 ` Dr. David Alan Gilbert
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