KVM: x86: Emulate MSR_EBC_FREQUENCY_ID

Some operating systems store data about the host processor at the
time of installation, and when booted on a more uptodate cpu tries
to read MSR_EBC_FREQUENCY_ID. This has been found with XP.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f47db2588a41..9d434777154d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1651,6 +1651,20 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
         case 0xcd: /* fsb frequency */
                 data = 3;
                 break;
+                /*
+                 * MSR_EBC_FREQUENCY_ID
+                 * Conservative value valid for even the basic CPU models.
+                 * Models 0,1: 000 in bits 23:21 indicating a bus speed of
+                 * 100MHz, model 2 000 in bits 18:16 indicating 100MHz,
+                 * and 266MHz for model 3, or 4. Set Core Clock
+                 * Frequency to System Bus Frequency Ratio to 1 (bits
+                 * 31:24) even though these are only valid for CPU
+                 * models > 2, however guests may end up dividing or
+                 * multiplying by zero otherwise.
+                 */
+        case MSR_EBC_FREQUENCY_ID:
+                data = 1 << 24;
+                break;
         case MSR_IA32_APICBASE:
                 data = kvm_get_apic_base(vcpu);
                 break;