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SubjectRe: [RFC PATCH 3/3] x86/cpu/amd, kvm: Satisfy guest kernel reads of IC_CFG MSR
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On 14/11/2015 11:37, Borislav Petkov wrote:
> From: Borislav Petkov <bp@suse.de>
>
> The kernel accesses IC_CFG MSR (0xc0011021) on AMD because it checks
> whether the way access filter is enabled on some F15h models, and, if
> so, disables it.
>
> kvm doesn't handle that MSR access and complains about it, which can
> get really noisy in dmesg when one starts kvm guests all the time for
> testing. And it is useless anyway - guest kernel shouldn't be doing such
> changes anyway so tell it that that filter is disabled.
>
> Signed-off-by: Borislav Petkov <bp@suse.de>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/include/asm/msr-index.h | 1 +
> arch/x86/kernel/cpu/amd.c | 4 ++--
> arch/x86/kvm/svm.c | 17 +++++++++++++++++
> 3 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
> index 9f3905697f12..5384485f8569 100644
> --- a/arch/x86/include/asm/msr-index.h
> +++ b/arch/x86/include/asm/msr-index.h
> @@ -322,6 +322,7 @@
> #define MSR_F15H_PERF_CTR 0xc0010201
> #define MSR_F15H_NB_PERF_CTL 0xc0010240
> #define MSR_F15H_NB_PERF_CTR 0xc0010241
> +#define MSR_F15H_IC_CFG 0xc0011021
>
> /* Fam 10h MSRs */
> #define MSR_FAM10H_MMIO_CONF_BASE 0xc0010058
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index 4a70fc6d400a..1d76dcdf7e55 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -665,9 +665,9 @@ static void init_amd_bd(struct cpuinfo_x86 *c)
> * Disable it on the affected CPUs.
> */
> if ((c->x86_model >= 0x02) && (c->x86_model < 0x20)) {
> - if (!rdmsrl_safe(0xc0011021, &value) && !(value & 0x1E)) {
> + if (!rdmsrl_safe(MSR_F15H_IC_CFG, &value) && !(value & 0x1E)) {
> value |= 0x1E;
> - wrmsrl_safe(0xc0011021, value);
> + wrmsrl_safe(MSR_F15H_IC_CFG, value);
> }
> }
> }
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 83a1c643f9a5..58b64c17c4a8 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -3053,6 +3053,23 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> case MSR_IA32_UCODE_REV:
> msr_info->data = 0x01000065;
> break;
> + case MSR_F15H_IC_CFG: {
> +
> + int family, model;
> +
> + family = guest_cpuid_family(vcpu);
> + model = guest_cpuid_model(vcpu);
> +
> + if (family < 0 || model < 0)
> + return kvm_get_msr_common(vcpu, msr_info);
> +
> + msr_info->data = 0;
> +
> + if (family == 0x15 &&
> + (model >= 0x2 && model < 0x20))
> + msr_info->data = 0x1E;
> + }
> + break;
> default:
> return kvm_get_msr_common(vcpu, msr_info);
> }
>

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>


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