This is a note to let you know that I've just added the patch titled

KVM: x86: pvclock: Handle first-time write to pvclock-page contains random junk

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: kvm-x86-pvclock-handle-first-time-write-to-pvclock-page-contains-random-junk.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 51c4b8bba674cfd2260d173602c4dac08e4c3a99 Mon Sep 17 00:00:00 2001

From: Liran Alon liran.alon@oracle.com Date: Sun, 5 Nov 2017 16:11:30 +0200 Subject: KVM: x86: pvclock: Handle first-time write to pvclock-page contains random junk MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

From: Liran Alon liran.alon@oracle.com

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

--- arch/x86/kvm/x86.c | 3 +++ 1 file changed, 3 insertions(+)

--- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1812,6 +1812,9 @@ static int kvm_guest_time_update(struct */ 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,

Patches currently in stable-queue which might be from liran.alon@oracle.com are

queue-4.4/kvm-x86-exit-to-user-mode-on-ud-intercept-when-emulator-requires.patch queue-4.4/kvm-x86-pvclock-handle-first-time-write-to-pvclock-page-contains-random-junk.patch