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.
Thanks,
Paolo
