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

From: Steve Rutherford
Date: Fri May 29 2020 - 22:08:29 EST

On Tue, May 5, 2020 at 2:19 PM Ashish Kalra <Ashish.Kalra@xxxxxxx> wrote:
>
> From: Ashish Kalra <ashish.kalra@xxxxxxx>
>
> 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@xxxxxxx>
> ---
> 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@xxxxxxxxxx>