[PATCH RFC 1/2] qemu: use "-accel" option to specify accelerator instead of "-machine"
jdenemar at redhat.com
Mon Jan 11 09:27:38 UTC 2021
On Mon, Jan 11, 2021 at 10:14:58 +0100, Paolo Bonzini wrote:
> On 11/01/21 09:35, JÃ¡n Tomko wrote:
> >> This unfortunately cannot be done unconditionally.Â You need to probe
> >> for the availability of -accel, using something like
> > What are we probing for?
> Existence of "-accel". "-accel" allows configuration of
> accelerator-specific, machine-independent properties. In the past they
> went in -machine but the two have been separate since 5.0 (with
> backwards-compatible glue).
> There were two phases of -accel support in QEMU:
> - 2.9 to 4.2: only one -accel option supported; specifying a fallback
> couldn't be done with -accel and required the older "-machine
> accel=tcg:kvm" instead
> - 5.0 or newer: multiple -accel options supported, e.g. "-accel tcg
> -accel kvm"
> and it would be possible to distinguish them, for example using QOM
> properties. However Libvirt only ever specifies one accelerator so it
> makes no difference.
We use a fallback for capabilities probing (in qemuProcessQMPLaunch) so
in case the old -machine type,accel=... way is going to be deprecated,
we need to be able to detect whether multiple -accel options are allowed
and use -machine otherwise.
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