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authorZachary Amsden <zamsden@redhat.com>2011-05-04 09:31:29 -0300
committerGreg Kroah-Hartman <gregkh@suse.de>2011-05-09 15:55:42 -0700
commitf413fc28a1db54519b75f731a6e57d1ef0269d78 (patch)
tree7ee28526ce50141217b8dc820f15625164d245d5
parentad2088cabe0fd7f633f38ba106025d33ed9a2105 (diff)
KVM: x86: Fix kvmclock bug
(backported from commit 28e4639adf0c9f26f6bb56149b7ab547bf33bb95) If preempted after kvmclock values are updated, but before hardware virtualization is entered, the last tsc time as read by the guest is never set. It underflows the next time kvmclock is updated if there has not yet been a successful entry / exit into hardware virt. Fix this by simply setting last_tsc to the newly read tsc value so that any computed nsec advance of kvmclock is nulled. Signed-off-by: Zachary Amsden <zamsden@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> BugLink: http://bugs.launchpad.net/bugs/714335 Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com> Reviewed-by: Stefan Bader <stefan.bader@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--arch/x86/kvm/x86.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8a10f27233af..df1cefb9457d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -694,6 +694,7 @@ static void kvm_write_guest_time(struct kvm_vcpu *v)
vcpu->hv_clock.tsc_timestamp = tsc_timestamp;
vcpu->hv_clock.system_time = kernel_ns + v->kvm->arch.kvmclock_offset;
vcpu->last_kernel_ns = kernel_ns;
+ vcpu->last_guest_tsc = tsc_timestamp;
/*
* The interface expects us to write an even number signaling that the