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>
(cherry picked from commit 2ecf91b6d8b0ee8ef38aa7ea2a0fe0cd57b6ca50)
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index f429a405f9f47560f5e83b121521d5f4b639efde..ebffde411c7794ee78499489bb171e4d202409e0 100644 (file)
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1048,6 +1048,7 @@ 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))