On 25/05/21 08:23, Vitaly Kuznetsov wrote:
Should it also disable APICv unconditionally if
HV_DEPRECATING_AEOI_RECOMMENDED is not in the guest CPUID? That should
avoid ping-pong between enabled and disabled APICv even in pathological
cases that we cannot think about.
When you run Hyper-V on KVM it doesn't use SynIC (let alone AutoEOI) but
we still inhibit APICv unconditionally. The patch as-is improves this
without any userspace changes required and I see it as a benefit. Going
forward, we will definitely add something like 'hv-synic-noaeoi' to QEMU
to make non-nesting setups benefit too but it'll take a while for this
option to propagate to real world configurations (sigh).
Ok, if enable<->disable APICv becomes an issue we can also consider
disabling APICv forever if AutoEOI is ever used.
Paolo
