Re: [RFC PATCH 0/2] MTE support for KVM guest

Catalin Marinas
2020-06-24T09:38:53Z

On Tue, Jun 23, 2020 at 07:05:07PM +0100, Peter Maydell wrote:
> On Wed, 17 Jun 2020 at 13:39, Steven Price <steven.price@arm.com> wrote:
> > These patches add support to KVM to enable MTE within a guest. It is
> > based on Catalin's v4 MTE user space series[1].
> >
> > [1] http://lkml.kernel.org/r/20200515171612.1020-1-catalin.marinas%40arm.com
> >
> > Posting as an RFC as I'd like feedback on the approach taken.
>
> What's your plan for handling tags across VM migration?
> Will the kernel expose the tag ram to userspace so we
> can copy it from the source machine to the destination
> at the same time as we copy the actual ram contents ?

Qemu can map the guest memory with PROT_MTE and access the tags directly
with LDG/STG instructions. Steven was actually asking in the cover
letter whether we should require that the VMM maps the guest memory with
PROT_MTE as a guarantee that it can access the guest tags.

There is no architecturally visible tag ram (tag storage), that's a
microarchitecture detail.

--
Catalin