On 16/11/2017 13:12, Quan Xu wrote: > However it seems there is still some gap.. > > as Rik said, "at context switch time, the context switch code will save > the guest FPU state to current->thread.fpu when the VCPU thread is scheduled out." By "guest FPU state" Rik means "guest FPU with host PKRU". Guest PKRU is always stored in vcpu->arch.pkru rather than in the guest FPU state, so guest PKRU will never be in current->thread.fpu.state either. KVM_GET_XSAVE will the guest FPU state with vcpu->arch.pkru and migration will work properly. Thanks, Paolo > after preempt_enable() in vcpu_enter_guest(), the vcpu thread is > scheduled out, > in kvm_x86_ops->run, the PKRU has been restored with host_pkru (IF > guest_pkru != host_pkru).. > instead of guest_pkru.. > > then the PKRU is host_pkru, how to save guest_pkru current->thread.fpu? > > as mentioned, all this _assumes_ that the pkru is in > current->thread.fpu.state as well. > > > thanks, > > Quan > Alibaba Cloud > >> Context switching will only happen in vcpu_enter_guest() after >> preempt_enable() for a preemptible kernel, or in vcpu_run via >> cond_resched() for a non-preemptible kernel. >> >> Thanks, >> >> Paolo >> >>> VM migration again, in case, >>> source_host_pkru_value != guest_pkru_value, >>> target_host_pkru_value == guest_pkru_value.. >>> >>> the pkru status would be inconsistent.. >> >
