KVM: allow bit 10 to be cleared in MSR_IA32_MC4_CTL
There is a quirk for AMD K8 CPUs in many Linux kernels (see
arch/x86/kernel/cpu/mcheck/mce.c:__mcheck_cpu_apply_quirks()) that
clears bit 10 in that MCE related MSR. KVM can only cope with all
zeros or all ones, so it will inject a #GP into the guest, which
will let it panic.
So lets add a quirk to the quirk and ignore this single cleared bit.
This fixes -cpu kvm64 on all machines and -cpu host on K8 machines
with some guest Linux kernels.
Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8f9b08d..9ad3d06 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -940,9 +940,13 @@
if (msr >= MSR_IA32_MC0_CTL &&
msr < MSR_IA32_MC0_CTL + 4 * bank_num) {
u32 offset = msr - MSR_IA32_MC0_CTL;
- /* only 0 or all 1s can be written to IA32_MCi_CTL */
+ /* only 0 or all 1s can be written to IA32_MCi_CTL
+ * some Linux kernels though clear bit 10 in bank 4 to
+ * workaround a BIOS/GART TBL issue on AMD K8s, ignore
+ * this to avoid an uncatched #GP in the guest
+ */
if ((offset & 0x3) == 0 &&
- data != 0 && data != ~(u64)0)
+ data != 0 && (data | (1 << 10)) != ~(u64)0)
return -1;
vcpu->arch.mce_banks[offset] = data;
break;