xen: suppress known wrmsrs

In general, Xen doesn't support wrmsr from an unprivileged domain; it
just ends up ignoring the instruction and printing a message on the
console.

Given that there are sets of MSRs we know the kernel will try to write
to, but we don't care, just eat them in xen_write_msr to cut down on
console noise.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index b011e4a5dbb..b795470ec06 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -854,6 +854,19 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
                         ret = -EFAULT;
                 break;
 #endif
+
+        case MSR_STAR:
+        case MSR_CSTAR:
+        case MSR_LSTAR:
+        case MSR_SYSCALL_MASK:
+        case MSR_IA32_SYSENTER_CS:
+        case MSR_IA32_SYSENTER_ESP:
+        case MSR_IA32_SYSENTER_EIP:
+                /* Fast syscall setup is all done in hypercalls, so
+                   these are all ignored.  Stub them out here to stop
+                   Xen console noise. */
+                break;
+
         default:
                 ret = native_write_msr_safe(msr, low, high);
         }