Re: [PATCH v6 1/3] ioreq: switch ioreq page allocation to vmap

On Tue, Aug 25, 2026 at 3:20 PM Julian Vetter <[email protected]> wrote:
> Thank you again for your feedback! I will wait then for Anthony's
> decision regarding whether the multi-page ioreq support and the ioreq_t
> growth should be combined into a single effort, before I proceed further
> with a v7.

BTW, if we're considering modifying the ioreq server protocol, I have
a few requests to consider from an ASI perspective.

Basically, at the moment, ioreq vcpu rings are grouped by backend; so
each vcpu shares a ring with all other vcpus; meaning that, in theory,
one vcpu could read the payload of another vcpu's IO operations.  This
isn't critical, but the more isolation the better.

What would be more convenient from an ASI perspective would be to have
per-vcpu data shared on separate pages.  One design would be to have a
single ioreq page per vcpu, with all ioreq server rings on the single
page.  What would perhaps be nicer long-term is to figure out a way
for all per-vcpu shared structures to share a single page (or set of
pages).

Not sure how this fits with the ioreq_t growth or multi-page ioreq
support, but thought it would be worthwhile to toss out there for
consideration:  At least to make ioreq page isolation less difficult,
and perhaps to make it easier.

 -George