Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: > On 12/27/21 18:32, Igor Mammedov wrote: >>> Tweaked and queued nevertheless, thanks. >> it seems this patch breaks VCPU hotplug, in scenario: >> >> 1. hotunplug existing VCPU (QEMU stores VCPU file descriptor in parked cpus list) >> 2. hotplug it again (unsuspecting QEMU reuses stored file descriptor when recreating VCPU) >> >> RHBZ:https://bugzilla.redhat.com/show_bug.cgi?id=2028337#c11 >> > > The fix here would be (in QEMU) to not call KVM_SET_CPUID2 again. > However, we need to work around it in KVM, and allow KVM_SET_CPUID2 if > the data passed to the ioctl is the same that was set before. Are we sure the data is going to be *exactly* the same? In particular, when using vCPU fds from the parked list, do we keep the same APIC/x2APIC id when hotplugging? Or can we actually hotplug with a different id? -- Vitaly
