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.

---
arch/x86/xen/enlighten.c | 13 +++++++++++++

1 file changed, 13 insertions(+)

===================================================================

@@ -803,6 +803,19 @@

			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);
	}

applied to tip/x86/xen - thanks,

Ingo