[PATCH] qemu: support kvm-pv-ipi off

[Michal Prívozník]

On 10/27/21 9:04 AM, zhenwei pi wrote:
> QEMU version 3.1 introduced PV_SEND_IPI CPUID feature bit under
> commit 7f710c32bb8 (target-i386: adds PV_SEND_IPI CPUID feature bit).
> 
> This patch adds a new KVM feature 'pv-ipi' to disable this feature
> (enabled by default). Newer CPU platform (Ex, AMD Zen2) supports
> hardware accelation for IPI in guest, to use this feature to get
> better performance in some scenarios. Detailed about the discussion:
>   https://lkml.org/lkml/2021/10/20/423
> 
> To disable kvm-pv-ipi and have libvirt add "-cpu host,kvm-pv-ipi=off"
> to the QEMU command line, the following XML code needs to be added to the
> guest's domain description:
> 
>   <features>
>     <kvm>
>       <pv-ipi state='off'/>
>     </kvm>
>   </features>
> 
> Signed-off-by: zhenwei pi <pizhenwei at bytedance.com>
> ---
>  docs/formatdomain.rst         | 2 ++
>  docs/schemas/domaincommon.rng | 5 +++++
>  src/conf/domain_conf.c        | 3 +++
>  src/conf/domain_conf.h        | 1 +
>  src/qemu/qemu_command.c       | 5 +++++
>  5 files changed, 16 insertions(+)

Patch looks good to me. But can you please send a follow up patch that
adds a test case? You can take an inspiration from here:

https://gitlab.com/libvirt/libvirt/-/commit/ea21b8b87b9ae72d0d9ebab10a1c5b1480f5a16a

Meanwhile, I'll merge this.

Reviewed-by: Michal Privoznik <mprivozn at redhat.com>

Michal