KVM: x86: relax MSR_KVM_SYSTEM_TIME alignment check

[Marcelo Tosatti <mtosatti@redhat.com>]

RHEL5 i386 guests register non 32-byte aligned addresses:

kvm-clock: cpu 1, msr 0:3018aa5, secondary cpu clock
kvm-clock: cpu 2, msr 0:301f8e9, secondary cpu clock
kvm-clock: cpu 3, msr 0:302672d, secondary cpu clock

Check for an address+len that would cross page boundary
instead.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f19ac0a..ad36d386 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1952,8 +1952,9 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 
 		gpa_offset = data & ~(PAGE_MASK | 1);
 
-		/* Check that the address is 32-byte aligned. */
-		if (gpa_offset & (sizeof(struct pvclock_vcpu_time_info) - 1))
+		/* Check that address+len does not cross page boundary */
+		if ((gpa_offset + sizeof(struct pvclock_vcpu_time_info) - 1)
+		    & PAGE_MASK)
 			break;
 
 		if (kvm_gfn_to_hva_cache_init(vcpu->kvm,