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>

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index b011e4a5dbbe6c1fed33053a077a094ded4313af..b795470ec06919da489b2260c49c67e42ae0abcd 100644 (file)
--- 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);
        }