[PATCH 3/4] [PATCH] kvmclock: allow it to be turned off

[Glauber Costa <gcosta@redhat.com>]

Use the lower 3 lower bits of the system time msr to turn off the clock.
This means that all clock registration has to be aligned in a 4-byte boundary

Signed-off-by: Glauber Costa <gcosta@redhat.com>
---
 arch/x86/kvm/x86.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6abd784..7ce14ce 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -591,6 +591,11 @@ int kvm_set_msr_common(struct kvm_vcpu *
 		if (vcpu->arch.time_page)
 			kvm_release_page_dirty(vcpu->arch.time_page);
 
+		/* 4-byte unaligned accesses are invalid */
+		if (data & 0x7) {
+			vcpu->arch.time_page = NULL;
+			break;
+		}
 		vcpu->arch.time = data & PAGE_MASK;
 		vcpu->arch.time_offset = data & ~PAGE_MASK;
 
-- 
1.4.2


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