From: Liran Alon Date: Sun, 5 Nov 2017 14:11:30 +0000 (+0200) Subject: KVM: x86: pvclock: Handle first-time write to pvclock-page contains random junk X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=ab29b6b818aa1cc8c36fc510464c732d392f5df2;p=sagit-ice-cold%2Fkernel_xiaomi_msm8998.git 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 Reviewed-by: Nikita Leshenko Reviewed-by: Konrad Rzeszutek Wilk Signed-off-by: Konrad Rzeszutek Wilk Reviewed-by: Paolo Bonzini Signed-off-by: Radim Krčmář Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 3ffd5900da5b..6a624989b13e 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1812,6 +1812,9 @@ static int kvm_guest_time_update(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,