From: Liran Alon <liran.alon@oracle.com>
To: pbonzini@redhat.com, rkrcmar@redhat.com, kvm@vger.kernel.org
Cc: idan.brown@oracle.com, Liran Alon <liran.alon@oracle.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: [PATCH] KVM: x86: pvclock: Handle first-time write to pvclock-page contains random junk
Date: Sun, 5 Nov 2017 16:11:30 +0200 [thread overview]
Message-ID: <1509891090-8985-1-git-send-email-liran.alon@oracle.com> (raw)
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>
---
arch/x86/kvm/x86.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 03869eb7fcd6..181106080e41 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1830,6 +1830,9 @@ 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,
--
1.9.1
next reply other threads:[~2017-11-05 14:11 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-05 14:11 Liran Alon [this message]
2017-11-06 9:13 ` [PATCH] KVM: x86: pvclock: Handle first-time write to pvclock-page contains random junk Paolo Bonzini
2017-11-10 21:36 ` Radim Krčmář
2017-11-13 0:40 ` Wanpeng Li
2017-11-13 0:44 ` Liran Alon
2017-11-13 0:52 ` Wanpeng Li
2017-11-13 0:55 ` Liran Alon
2017-11-13 1:03 ` Wanpeng Li
2017-11-13 1:37 ` Wanpeng Li
2017-11-13 5:53 ` Wanpeng Li
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