Sean Christopherson <seanjc@xxxxxxxxxx> writes:
> Move the few bits of relevant fx_init() code into kvm_arch_vcpu_create(),
> dropping the superfluous check on vcpu->arch.guest_fpu that was blindly
> and wrongly added by commit ed02b213098a ("KVM: SVM: Guest FPU state
> save/restore not needed for SEV-ES guest").
I have more questions to the above mentioned commit: why is it OK to
'return 0' from kvm_vcpu_ioctl_x86_set_xsave() without writing anything
to 'guest_xsave'? Same goes to kvm_arch_vcpu_ioctl_get_fpu(). Whould't
it be better to throw an error as we can't actually get this information
for encrypted guests? It's probably too late to change this now I
suppose ...
>
> Note, KVM currently allocates and then frees FPU state for SEV-ES guests,
> rather than avoid the allocation in the first place. While that approach
> is inarguably inefficient and unnecessary, it's a cleanup for the future.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 16 ++++------------
> 1 file changed, 4 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 6fd3fe21863e..ec61b90d9b73 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10614,17 +10614,6 @@ static int sync_regs(struct kvm_vcpu *vcpu)
> return 0;
> }
>
> -static void fx_init(struct kvm_vcpu *vcpu)
> -{
> - if (!vcpu->arch.guest_fpu)
> - return;
> -
> - fpstate_init(&vcpu->arch.guest_fpu->state);
> - if (boot_cpu_has(X86_FEATURE_XSAVES))
> - vcpu->arch.guest_fpu->state.xsave.header.xcomp_bv =
> - host_xcr0 | XSTATE_COMPACTION_ENABLED;
> -}
> -
> void kvm_free_guest_fpu(struct kvm_vcpu *vcpu)
> {
> if (vcpu->arch.guest_fpu) {
> @@ -10703,7 +10692,10 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
> pr_err("kvm: failed to allocate vcpu's fpu\n");
> goto free_user_fpu;
> }
> - fx_init(vcpu);
> + fpstate_init(&vcpu->arch.guest_fpu->state);
> + if (boot_cpu_has(X86_FEATURE_XSAVES))
> + vcpu->arch.guest_fpu->state.xsave.header.xcomp_bv =
> + host_xcr0 | XSTATE_COMPACTION_ENABLED;
>
> vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
> vcpu->arch.reserved_gpa_bits = kvm_vcpu_reserved_gpa_bits_raw(vcpu);
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
--
Vitaly
