Re: [PATCH v4 5/5] x86, kvm: support vcpu preempted check

2016-10-24 16:39+0200, Paolo Bonzini:

On 19/10/2016 19:24, Radim Krčmář wrote:

quoted

quoted

quoted

+	if (vcpu->arch.st.msr_val & KVM_MSR_ENABLED)
+		if (kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
+					&vcpu->arch.st.steal,
+					sizeof(struct kvm_steal_time)) == 0) {
+			vcpu->arch.st.steal.preempted = 1;
+			kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
+					&vcpu->arch.st.steal,
+					sizeof(struct kvm_steal_time));
+		}

Please name this block of code.  Something like
  kvm_steal_time_set_preempted(vcpu);

While at it:

1) the kvm_read_guest_cached is not necessary.  You can rig the call to
kvm_write_guest_cached so that it only writes vcpu->arch.st.steal.preempted.

I agree.  kvm_write_guest_cached() always writes from offset 0, so we'd
want a new function that allows to specify a starting offset.

Using cached vcpu->arch.st.steal to avoid the read wouldn't be as good.