KVM: x86: expose MSR_TSC_AUX to userspace

commit 9dbe6cf941a6fe82933aef565e4095fb10f65023 upstream.

If we do not do this, it is not properly saved and restored across
migration.  Windows notices due to its self-protection mechanisms,
and is very upset about it (blue screen of death).

Cc: Radim Krcmar <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[bwh: Backported to 3.2:
 - We didn't yet have the switch() in kvm_init_msr_list as MPX is not
   supported at all
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 80c6d68..d47d153 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -834,7 +834,8 @@ static u32 msrs_to_save[] = {
 #ifdef CONFIG_X86_64
        MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR,
 #endif
-       MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA
+       MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA,
+       MSR_TSC_AUX,
 };
 
 static unsigned num_msrs_to_save;
@@ -3867,6 +3868,20 @@ static void kvm_init_msr_list(void)
        for (i = j = KVM_SAVE_MSRS_BEGIN; i < ARRAY_SIZE(msrs_to_save); i++) {
                if (rdmsr_safe(msrs_to_save[i], &dummy[0], &dummy[1]) < 0)
                        continue;
+
+               /*
+                * Even MSRs that are valid in the host may not be exposed
+                * to the guests in some cases.
+                */
+               switch (msrs_to_save[i]) {
+               case MSR_TSC_AUX:
+                       if (!kvm_x86_ops->rdtscp_supported())
+                               continue;
+                       break;
+               default:
+                       break;
+               }
+
                if (j < i)
                        msrs_to_save[j] = msrs_to_save[i];
                j++;