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authorLiran Alon <liran.alon@oracle.com>2017-11-05 16:11:30 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-12-05 11:24:33 +0100
commitf5477da6c3b0f8df578a55dfdeebe18458303e4d (patch)
tree946366ed000a0b0307e00a14f63afb24d5822ca9 /arch
parente18a963b36a001b0067f9091b4ea23aa152af341 (diff)
KVM: x86: pvclock: Handle first-time write to pvclock-page contains random junk
commit 51c4b8bba674cfd2260d173602c4dac08e4c3a99 upstream. When guest passes KVM it's pvclock-page GPA via WRMSR to MSR_KVM_SYSTEM_TIME / MSR_KVM_SYSTEM_TIME_NEW, KVM don't initialize pvclock-page to some start-values. It just requests a clock-update which will happen before entering to guest. The clock-update logic will call kvm_setup_pvclock_page() to update the pvclock-page with info. However, kvm_setup_pvclock_page() *wrongly* assumes that the version-field is initialized to an even number. This is wrong because at first-time write, field could be any-value. Fix simply makes sure that if first-time version-field is odd, increment it once more to make it even and only then start standard logic. This follows same logic as done in other pvclock shared-pages (See kvm_write_wall_clock() and record_steal_time()). Signed-off-by: Liran Alon <liran.alon@oracle.com> Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/x86.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 595f8149c0d9..a4294fd1caa7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1797,6 +1797,9 @@ static void kvm_setup_pvclock_page(struct kvm_vcpu *v)
*/
BUILD_BUG_ON(offsetof(struct pvclock_vcpu_time_info, version) != 0);
+ if (guest_hv_clock.version & 1)
+ ++guest_hv_clock.version; /* first time write, random junk */
+
vcpu->hv_clock.version = guest_hv_clock.version + 1;
kvm_write_guest_cached(v->kvm, &vcpu->pv_time,
&vcpu->hv_clock,