xen/x86: Don't try to write syscall-related MSRs for PV guests

For PV guests these registers are set up by hypervisor and thus
should not be written by the guest. The comment in xen_write_msr_safe()
says so but we still write the MSRs, causing the hypervisor to
print a warning.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 30d12afe52ed..1f1dbd2949a4 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1077,6 +1077,7 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
                 /* Fast syscall setup is all done in hypercalls, so
                    these are all ignored.  Stub them out here to stop
                    Xen console noise. */
+                break;
 
         default:
                 if (!pmu_msr_write(msr, low, high, &ret))