KVM: x86: TSC reset compensation

Attempt to synchronize TSCs which are reset to the same value.  In the
case of a reliable hardware TSC, we can just re-use the same offset, but
on non-reliable hardware, we can get closer by adjusting the offset to
match the elapsed time.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a215153..57b4394 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -396,6 +396,9 @@
 	unsigned long irq_sources_bitmap;
 	s64 kvmclock_offset;
 	spinlock_t tsc_write_lock;
+	u64 last_tsc_nsec;
+	u64 last_tsc_offset;
+	u64 last_tsc_write;
 
 	struct kvm_xen_hvm_config xen_hvm_config;