Re: [PATCH RFC 1/2] qemu: use "-accel" option to specify accelerator instead of "-machine"

On 11/01/21 09:35, Ján Tomko wrote: >> This unfortunately cannot be done unconditionally.  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.