On 2/14/22 10:43, David Edmondson wrote:
Sorry if this is a daft question:
In what situations will there be bits set in
vcpu->arch.guest_supported_xcr0 that are not set in
vcpu->arch.guest_fpu.fpstate->xfeatures ?
guest_supported_xcr0 is filtered based on supported_xcr0, which I would
expect to weed out all bits that are not set in ->xfeatures.
Good point, so we can do just
vcpu->arch.guest_fpu.fpstate->user_xfeatures =
vcpu->arch.guest_supported_xcr0;
On top of this patch, we can even replace vcpu->arch.guest_supported_xcr0
with vcpu->arch.guest_fpu.fpstate->user_xfeatures. Probably with local
variables or wrapper functions though, so as to keep the code readable.
For example:
static inline u64 kvm_guest_supported_xfd()
{
u64 guest_supported_xcr0 = vcpu->arch.guest_fpu.fpstate->user_xfeatures;
return guest_supported_xcr0 & XFEATURE_MASK_USER_DYNAMIC;
}
Also, already in this patch fpstate_realloc should do
newfps->user_xfeatures = curfps->user_xfeatures | xfeatures;
only if !guest_fpu. In other words, the user_xfeatures of the guest FPU
should be controlled exclusively by KVM_SET_CPUID2.
Thanks,
Paolo
