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KVM: x86: retain pvclock guest stopped bit in guest memory

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Otherwise its possible for an unrelated KVM_REQ_UPDATE_CLOCK (such as due to CPU
migration) to clear the bit.

Noticed by Paolo Bonzini.

Reviewed-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Marcelo Tosatti 2012-11-27 23:28:47 -02:00
parent 807f12e57c
commit 78c0337a38
1 changed files with 13 additions and 7 deletions
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20
arch/x86/kvm/x86.c
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@ -1145,6 +1145,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
unsigned long this_tsc_khz;
s64 kernel_ns, max_kernel_ns;
u64 tsc_timestamp;
struct pvclock_vcpu_time_info *guest_hv_clock;
u8 pvclock_flags;
/* Keep irq disabled to prevent changes to the clock */
@ -1228,13 +1229,6 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
vcpu->last_kernel_ns = kernel_ns;
vcpu->last_guest_tsc = tsc_timestamp;
pvclock_flags = 0;
if (vcpu->pvclock_set_guest_stopped_request) {
pvclock_flags |= PVCLOCK_GUEST_STOPPED;
vcpu->pvclock_set_guest_stopped_request = false;
}
vcpu->hv_clock.flags = pvclock_flags;
/*
* The interface expects us to write an even number signaling that the
@ -1245,6 +1239,18 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
shared_kaddr = kmap_atomic(vcpu->time_page);
guest_hv_clock = shared_kaddr + vcpu->time_offset;
/* retain PVCLOCK_GUEST_STOPPED if set in guest copy */
pvclock_flags = (guest_hv_clock->flags & PVCLOCK_GUEST_STOPPED);
if (vcpu->pvclock_set_guest_stopped_request) {
pvclock_flags |= PVCLOCK_GUEST_STOPPED;
vcpu->pvclock_set_guest_stopped_request = false;
}
vcpu->hv_clock.flags = pvclock_flags;
memcpy(shared_kaddr + vcpu->time_offset, &vcpu->hv_clock,
sizeof(vcpu->hv_clock));