[PATCH] x86/msr: handle IA32_THERM_STATUS

[Roger Pau Monne <roger.pau@citrix.com>]

Windows 8 will attempt to read MSR_IA32_THERM_STATUS and panic if a
#GP fault is injected as a result:

vmx.c:3035:d8v0 RDMSR 0x0000019c unimplemented
d8v0 VIRIDIAN CRASH: 3b c0000096 fffff8061de31651 fffff4088a613720 0

So handle the MSR and return 0 instead.

Note that this is done on the generic MSR handler, and PV guest will
also get 0 back when trying to read the MSR. There doesn't seem to be
much value in handling the MSR for HVM guests only.

Fixes: 84e848fd7a1 ('x86/hvm: disallow access to unknown MSRs')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
 xen/arch/x86/msr.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index e4c4fa6127..190d6ac6c5 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -253,6 +253,12 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
             break;
         goto gp_fault;
 
+    case MSR_IA32_THERM_STATUS:
+        if ( cp->x86_vendor != X86_VENDOR_INTEL )
+            goto gp_fault;
+        *val = 0;
+        break;
+
     case MSR_X2APIC_FIRST ... MSR_X2APIC_LAST:
         if ( !is_hvm_domain(d) || v != curr )
             goto gp_fault;
-- 
2.28.0