On 15.11.2017 12:43, Liran Alon wrote:
> This MSR returns the number of #SMIs that occurred on CPU since
> boot.
>
> It was seen to be used frequently by ESXi guest.
>
> Patch adds a new vcpu-arch specific var called smi_count to
> save the number of #SMIs which occurred on CPU since boot.
> It is exposed as a read-only MSR to guest (causing #GP
> on wrmsr) in RDMSR/WRMSR emulation code.
> MSR_SMI_COUNT is also added to emulated_msrs[] to make sure
> user-space can save/restore it for migration purposes.
>
> Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx>
> Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Reviewed-by: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>
> Reviewed-by: Bhavesh Davda <bhavesh.davda@xxxxxxxxxx>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
>
> Notes:
> To make vmsave/vload work for MSR_SMI_COUNT (for migration purposes),
> a patch for QEMU is also required.
> We have written such patch and verified that it works.
> It will be submitted seperately to the QEMU mailing list.
>
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/x86.c | 11 +++++++++++
> 2 files changed, 12 insertions(+)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index c73e493adf07..089856eeac5d 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -504,6 +504,7 @@ struct kvm_vcpu_arch {
> int mp_state;
> u64 ia32_misc_enable_msr;
> u64 smbase;
> + u64 smi_count;
> bool tpr_access_reporting;
> u64 ia32_xss;
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 21c00594f230..dedf5539f924 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1036,6 +1036,7 @@ bool kvm_rdpmc(struct kvm_vcpu *vcpu)
> MSR_IA32_MCG_CTL,
> MSR_IA32_MCG_EXT_CTL,
> MSR_IA32_SMBASE,
> + MSR_SMI_COUNT,
> MSR_PLATFORM_INFO,
> MSR_MISC_FEATURES_ENABLES,
> };
> @@ -2217,6 +2218,11 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> return 1;
> vcpu->arch.smbase = data;
> break;
> + case MSR_SMI_COUNT:
> + if (!msr_info->host_initiated)
> + return 1;
> + vcpu->arch.smi_count = data;
> + break;
> case MSR_KVM_WALL_CLOCK_NEW:
> case MSR_KVM_WALL_CLOCK:
> vcpu->kvm->arch.wall_clock = data;
> @@ -2491,6 +2497,9 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> return 1;
> msr_info->data = vcpu->arch.smbase;
> break;
> + case MSR_SMI_COUNT:
> + msr_info->data = vcpu->arch.smi_count;
> + break;
> case MSR_IA32_PERF_STATUS:
> /* TSC increment by tick */
> msr_info->data = 1000ULL;
> @@ -6437,6 +6446,7 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool req_int_win)
> kvm_x86_ops->queue_exception(vcpu);
> } else if (vcpu->arch.smi_pending && !is_smm(vcpu)) {
> vcpu->arch.smi_pending = false;
> + ++vcpu->arch.smi_count;
> enter_smm(vcpu);
> } else if (vcpu->arch.nmi_pending && kvm_x86_ops->nmi_allowed(vcpu)) {
> --vcpu->arch.nmi_pending;
> @@ -7781,6 +7791,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
> vcpu->arch.hflags = 0;
>
> vcpu->arch.smi_pending = 0;
> + vcpu->arch.smi_count = 0;
> atomic_set(&vcpu->arch.nmi_queued, 0);
> vcpu->arch.nmi_pending = 0;
> vcpu->arch.nmi_injected = false;
>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
(only wondering if we have to make availability depend on e.g. a
KVM_CAP, so a guest will not silently start using it, although migration
with old QEMUs is broken)
--
Thanks,
David / dhildenb
