Hi
On 02/19/2016 12:18 AM, Paolo Bonzini wrote:
On 18/02/2016 17:27, Radim Krčmář wrote:
2016-02-18 16:53+0100, Paolo Bonzini:
Patch 9 is okay, but it is also necessary to clear IsRunning in
kvm_arch_vcpu_blocking and set it in kvm_arch_vcpu_unblocking. In
addition, vcpu_put/vcpu_load should not modify IsRunning between
kvm_arch_vcpu_blocking and kvm_arch_vcpu_unblocking. Do you agree?
Yes.
I think we don't need to clear IsRunning on preemption, which would
simplify the protection. (I haven't thought much about userspace exit,
so maybe we could skip that one as well, but we don't need to now.)
The reason for that is that KVM knows that the VCPU was scheduled out,
so it couldn't do much in the AVIC VMEXIT.
(KVM could force scheduler to pritioritize the VCPU, but our kick
doesn't do that now and it seems like a bad idea.)
Does it seem reasonable?
Yes, and in fact it wouldn't need to clear and set IsRunning on
vcpu_put/vcpu_load; only on vcpu_blocking/vcpu_unblocking.
The IsRunning flag is more of a IsNotHalted flag, in the end.
Paolo
In facts, instead of setting up the vAPIC backing page address when
calling kvm_arch_vcpu_load(), we should be able to do it when calling
kvm_arch_vcpu_sched_in(). This seems more appropriate since the
kvm_arch_vcpu_load() is also called in many unnecessary occasions via
vcpu_load() (in the arch/x86/kvm/x86.c). The same goes for the
kvm_arch_vcpu_put().
However, there is no kvm_arch_vcpu_sched_out(). But that can be added
easily.
What do you think?
Suravee
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