[PATCH 1/2] ignore AMDs HWCR register access to set the FFDIS bit

[PATCH 1/2] ignore AMDs HWCR register access to set the FFDIS bit

[Andre Przywara]

Linux tries to disable the flush filter on all AMD K8 CPUs. Since KVM
does not handle the needed MSR, the injected #GP will panic the Linux
kernel. Ignore setting of the HWCR.FFDIS bit in this MSR to let Linux
boot with an AMD K8 family guest CPU.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
---
 arch/x86/kvm/x86.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5a66bb9..4c19c24 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -796,6 +796,13 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 	case MSR_EFER:
 		set_efer(vcpu, data);
 		break;
+	case MSR_K7_HWCR:
+		if (data != 0x40) {
+			pr_unimpl(vcpu, "unimplemented HWCR wrmsr: 0x%llx\n",
+				data);
+			return 1;
+		}
+		break;
 	case MSR_IA32_DEBUGCTLMSR:
 		if (!data) {
 			/* We support the non-activated case already */
-- 
1.6.1.3

Re: [PATCH 1/2] ignore AMDs HWCR register access to set the FFDIS bit

[Avi Kivity]

On 06/23/2009 01:20 AM, Andre Przywara wrote:
> Linux tries to disable the flush filter on all AMD K8 CPUs. Since KVM
> does not handle the needed MSR, the injected #GP will panic the Linux
> kernel. Ignore setting of the HWCR.FFDIS bit in this MSR to let Linux
> boot with an AMD K8 family guest CPU.
>
> Signed-off-by: Andre Przywara<andre.przywara@amd.com>
> ---
>   arch/x86/kvm/x86.c |    7 +++++++
>   1 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 5a66bb9..4c19c24 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -796,6 +796,13 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>   	case MSR_EFER:
>   		set_efer(vcpu, data);
>   		break;
> +	case MSR_K7_HWCR:
> +		if (data != 0x40) {
> +			pr_unimpl(vcpu, "unimplemented HWCR wrmsr: 0x%llx\n",
> +				data);
> +			return 1;
> +		}
> +		break;
>    

Won't that printk() if writing a zero?  Just mask out that bit.

I also see some HWCR handling in svm.c, can probably be removed.

-- 
error compiling committee.c: too many arguments to function