On Tue, Jan 18, 2022 at 02:06:55PM +0100, Paolo Bonzini wrote:
> Sorry, hit send on the wrong window. This is the only patch that
> will require a bit more work.
>
> On 1/18/22 13:52, Paolo Bonzini wrote:
> >>@@ -124,6 +150,8 @@ void x86_cpus_init(X86MachineState *x86ms,
> >>int default_cpu_version)
> >> MachineState *ms = MACHINE(x86ms);
> >> MachineClass *mc = MACHINE_GET_CLASS(x86ms);
> >>+ /* Request AMX pemission for guest */
> >>+ x86_xsave_req_perm();
> >> x86_cpu_set_default_version(default_cpu_version);
> >
> >This should be done before creating a CPU with support for state
> >component 18. It happens in kvm_init_vcpu, with the following
> >call stack:
> >
> > kvm_init_vcpu
> > kvm_vcpu_thread_fn
> > kvm_start_vcpu_thread
> > qemu_init_vcpu
> > x86_cpu_realizefn
> >
> >The issue however is that this has to be done before
> >KVM_GET_SUPPORTED_CPUID and KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2).
> >
> >For the former, you can assume that anything returned by
> >ARCH_GET_XCOMP_GUEST_PERM will be returned by
> >KVM_GET_SUPPORTED_CPUID in CPUID[0xD].EDX:EAX, so you can:
> >
> >- add it to kvm_arch_get_supported_cpuid
>
> ... together with the other special cases (otherwise
> x86_cpu_get_supported_feature_word complains that XTILEDATA is not
> available)
>
> - change kvm_cpu_xsave_init to use host_cpuid instead of
> kvm_arch_get_supported_cpuid.
>
> - call ARCH_REQ_XCOMP_GUEST_PERM from
> x86_cpu_enable_xsave_components, with a conditional like
>
> if (kvm_enabled()) {
> kvm_request_xsave_components(cpu, mask);
> }
>
> KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2) is actually not a problem; the
> ioctl is only called from kvm_arch_init_vcpu and therefore after
> x86_cpu_enable_xsave_components.
>
Paolo, thanks too much for those detailed steps!
I have completed the new patch according to those steps, and work well.
Since this is only big change patch, the next version will be removed RFC.
Thanks!
Yang
> Thanks,
>
> Paolo
