Re: [PATCH v8 13/18] KVM: x86: Introduce new KVM_FEATURE_SEV_LIVE_MIGRATION feature & Custom MSR.

[Steve Rutherford <srutherford@google.com>]

On Tue, May 5, 2020 at 2:19 PM Ashish Kalra <Ashish.Kalra@amd.com> wrote:
>
> From: Ashish Kalra <ashish.kalra@amd.com>
>
> Add new KVM_FEATURE_SEV_LIVE_MIGRATION feature for guest to check
> for host-side support for SEV live migration. Also add a new custom
> MSR_KVM_SEV_LIVE_MIG_EN for guest to enable the SEV live migration
> feature.
>
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> ---
>  Documentation/virt/kvm/cpuid.rst     |  5 +++++
>  Documentation/virt/kvm/msr.rst       | 10 ++++++++++
>  arch/x86/include/uapi/asm/kvm_para.h |  5 +++++
>  arch/x86/kvm/svm/sev.c               | 14 ++++++++++++++
>  arch/x86/kvm/svm/svm.c               | 16 ++++++++++++++++
>  arch/x86/kvm/svm/svm.h               |  2 ++
>  6 files changed, 52 insertions(+)
>
> diff --git a/Documentation/virt/kvm/cpuid.rst b/Documentation/virt/kvm/cpuid.rst
> index 01b081f6e7ea..0514523e00cd 100644
> --- a/Documentation/virt/kvm/cpuid.rst
> +++ b/Documentation/virt/kvm/cpuid.rst
> @@ -86,6 +86,11 @@ KVM_FEATURE_PV_SCHED_YIELD        13          guest checks this feature bit
>                                                before using paravirtualized
>                                                sched yield.
>
> +KVM_FEATURE_SEV_LIVE_MIGRATION    14          guest checks this feature bit before
> +                                              using the page encryption state
> +                                              hypercall to notify the page state
> +                                              change
> +
>  KVM_FEATURE_CLOCSOURCE_STABLE_BIT 24          host will warn if no guest-side
>                                                per-cpu warps are expeced in
>                                                kvmclock
> diff --git a/Documentation/virt/kvm/msr.rst b/Documentation/virt/kvm/msr.rst
> index 33892036672d..7cd7786bbb03 100644
> --- a/Documentation/virt/kvm/msr.rst
> +++ b/Documentation/virt/kvm/msr.rst
> @@ -319,3 +319,13 @@ data:
>
>         KVM guests can request the host not to poll on HLT, for example if
>         they are performing polling themselves.
> +
> +MSR_KVM_SEV_LIVE_MIG_EN:
> +        0x4b564d06
> +
> +       Control SEV Live Migration features.
> +
> +data:
> +        Bit 0 enables (1) or disables (0) host-side SEV Live Migration feature.
> +        Bit 1 enables (1) or disables (0) support for SEV Live Migration extensions.
> +        All other bits are reserved.
> diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
> index 2a8e0b6b9805..d9d4953b42ad 100644
> --- a/arch/x86/include/uapi/asm/kvm_para.h
> +++ b/arch/x86/include/uapi/asm/kvm_para.h
> @@ -31,6 +31,7 @@
>  #define KVM_FEATURE_PV_SEND_IPI        11
>  #define KVM_FEATURE_POLL_CONTROL       12
>  #define KVM_FEATURE_PV_SCHED_YIELD     13
> +#define KVM_FEATURE_SEV_LIVE_MIGRATION 14
>
>  #define KVM_HINTS_REALTIME      0
>
> @@ -50,6 +51,7 @@
>  #define MSR_KVM_STEAL_TIME  0x4b564d03
>  #define MSR_KVM_PV_EOI_EN      0x4b564d04
>  #define MSR_KVM_POLL_CONTROL   0x4b564d05
> +#define MSR_KVM_SEV_LIVE_MIG_EN        0x4b564d06
>
>  struct kvm_steal_time {
>         __u64 steal;
> @@ -122,4 +124,7 @@ struct kvm_vcpu_pv_apf_data {
>  #define KVM_PV_EOI_ENABLED KVM_PV_EOI_MASK
>  #define KVM_PV_EOI_DISABLED 0x0
>
> +#define KVM_SEV_LIVE_MIGRATION_ENABLED                 (1 << 0)
> +#define KVM_SEV_LIVE_MIGRATION_EXTENSIONS_SUPPORTED    (1 << 1)
> +
>  #endif /* _UAPI_ASM_X86_KVM_PARA_H */
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index c0d7043a0627..6f69c3a47583 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1469,6 +1469,17 @@ int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
>         return 0;
>  }
>
> +void sev_update_migration_flags(struct kvm *kvm, u64 data)
> +{
> +       struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> +
> +       if (!sev_guest(kvm))
> +               return;
> +
> +       if (data & KVM_SEV_LIVE_MIGRATION_ENABLED)
> +               sev->live_migration_enabled = true;
> +}
> +
>  int svm_get_page_enc_bitmap(struct kvm *kvm,
>                                    struct kvm_page_enc_bitmap *bmap)
>  {
> @@ -1481,6 +1492,9 @@ int svm_get_page_enc_bitmap(struct kvm *kvm,
>         if (!sev_guest(kvm))
>                 return -ENOTTY;
>
> +       if (!sev->live_migration_enabled)
> +               return -EINVAL;
> +
>         gfn_start = bmap->start_gfn;
>         gfn_end = gfn_start + bmap->num_pages;
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 442adbbb0641..a99f5457f244 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -2633,6 +2633,9 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
>                 svm->msr_decfg = data;
>                 break;
>         }
> +       case MSR_KVM_SEV_LIVE_MIG_EN:
> +               sev_update_migration_flags(vcpu->kvm, data);
> +               break;
>         case MSR_IA32_APICBASE:
>                 if (kvm_vcpu_apicv_active(vcpu))
>                         avic_update_vapic_bar(to_svm(vcpu), data);
> @@ -3493,6 +3496,19 @@ static void svm_cpuid_update(struct kvm_vcpu *vcpu)
>         svm->nrips_enabled = kvm_cpu_cap_has(X86_FEATURE_NRIPS) &&
>                              guest_cpuid_has(&svm->vcpu, X86_FEATURE_NRIPS);
>
> +        /*
> +         * If SEV guest then enable the Live migration feature.
> +         */
> +        if (sev_guest(vcpu->kvm)) {
> +              struct kvm_cpuid_entry2 *best;
> +
> +              best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0);
> +              if (!best)
> +                      return;
> +
> +              best->eax |= (1 << KVM_FEATURE_SEV_LIVE_MIGRATION);
> +        }
> +
>         if (!kvm_vcpu_apicv_active(vcpu))
>                 return;
>
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index fd99e0a5417a..77f132a6fead 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -65,6 +65,7 @@ struct kvm_sev_info {
>         int fd;                 /* SEV device fd */
>         unsigned long pages_locked; /* Number of pages locked */
>         struct list_head regions_list;  /* List of registered regions */
> +       bool live_migration_enabled;
>         unsigned long *page_enc_bmap;
>         unsigned long page_enc_bmap_size;
>  };
> @@ -494,5 +495,6 @@ int svm_unregister_enc_region(struct kvm *kvm,
>  void pre_sev_run(struct vcpu_svm *svm, int cpu);
>  int __init sev_hardware_setup(void);
>  void sev_hardware_teardown(void);
> +void sev_update_migration_flags(struct kvm *kvm, u64 data);
>
>  #endif
> --
> 2.17.1
>

Reviewed-by: Steve Rutherford <srutherford@google.com>