linux-kernel - [PATCH] xen: suppress known wrmsrs

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Date:	Thu, 24 Jul 2008 13:48:58 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] 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@...rix.com>
---
 arch/x86/xen/enlighten.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

===================================================================
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -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);
 	}


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