Re: [PATCH v12 10/13] KVM: x86: Introduce new KVM_FEATURE_SEV_LIVE_MIGRATION feature & Custom MSR.

[Steve Rutherford]

On Mon, Apr 12, 2021 at 12:46 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_MIGRATION for guest to enable the SEV live migration
> feature.
>
> MSR is handled by userspace using MSR filters.
>
> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
> ---
>  Documentation/virt/kvm/cpuid.rst     |  5 +++++
>  Documentation/virt/kvm/msr.rst       | 12 ++++++++++++
>  arch/x86/include/uapi/asm/kvm_para.h |  4 ++++
>  arch/x86/kvm/cpuid.c                 |  3 ++-
>  4 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/virt/kvm/cpuid.rst b/Documentation/virt/kvm/cpuid.rst
> index cf62162d4be2..0bdb6cdb12d3 100644
> --- a/Documentation/virt/kvm/cpuid.rst
> +++ b/Documentation/virt/kvm/cpuid.rst
> @@ -96,6 +96,11 @@ KVM_FEATURE_MSI_EXT_DEST_ID        15          guest checks this feature bit
>                                                 before using extended destination
>                                                 ID bits in MSI address bits 11-5.
>
> +KVM_FEATURE_SEV_LIVE_MIGRATION     16          guest checks this feature bit before
> +                                               using the page encryption state
> +                                               hypercall to notify the page state
> +                                               change
> +
>  KVM_FEATURE_CLOCKSOURCE_STABLE_BIT 24          host will warn if no guest-side
>                                                 per-cpu warps are expected in
>                                                 kvmclock
> diff --git a/Documentation/virt/kvm/msr.rst b/Documentation/virt/kvm/msr.rst
> index e37a14c323d2..020245d16087 100644
> --- a/Documentation/virt/kvm/msr.rst
> +++ b/Documentation/virt/kvm/msr.rst
> @@ -376,3 +376,15 @@ data:
>         write '1' to bit 0 of the MSR, this causes the host to re-scan its queue
>         and check if there are more notifications pending. The MSR is available
>         if KVM_FEATURE_ASYNC_PF_INT is present in CPUID.
> +
> +MSR_KVM_SEV_LIVE_MIGRATION:
> +        0x4b564d08
> +
> +       Control SEV Live Migration features.
> +
> +data:
> +        Bit 0 enables (1) or disables (0) host-side SEV Live Migration feature,
> +        in other words, this is guest->host communication that it's properly
> +        handling the shared pages list.
> +
> +        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 950afebfba88..f6bfa138874f 100644
> --- a/arch/x86/include/uapi/asm/kvm_para.h
> +++ b/arch/x86/include/uapi/asm/kvm_para.h
> @@ -33,6 +33,7 @@
>  #define KVM_FEATURE_PV_SCHED_YIELD     13
>  #define KVM_FEATURE_ASYNC_PF_INT       14
>  #define KVM_FEATURE_MSI_EXT_DEST_ID    15
> +#define KVM_FEATURE_SEV_LIVE_MIGRATION 16
>
>  #define KVM_HINTS_REALTIME      0
>
> @@ -54,6 +55,7 @@
>  #define MSR_KVM_POLL_CONTROL   0x4b564d05
>  #define MSR_KVM_ASYNC_PF_INT   0x4b564d06
>  #define MSR_KVM_ASYNC_PF_ACK   0x4b564d07
> +#define MSR_KVM_SEV_LIVE_MIGRATION     0x4b564d08
>
>  struct kvm_steal_time {
>         __u64 steal;
> @@ -136,4 +138,6 @@ 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 BIT_ULL(0)
> +
>  #endif /* _UAPI_ASM_X86_KVM_PARA_H */
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 6bd2f8b830e4..4e2e69a692aa 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -812,7 +812,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
>                              (1 << KVM_FEATURE_PV_SEND_IPI) |
>                              (1 << KVM_FEATURE_POLL_CONTROL) |
>                              (1 << KVM_FEATURE_PV_SCHED_YIELD) |
> -                            (1 << KVM_FEATURE_ASYNC_PF_INT);
> +                            (1 << KVM_FEATURE_ASYNC_PF_INT) |
> +                            (1 << KVM_FEATURE_SEV_LIVE_MIGRATION);
>
>                 if (sched_info_on())
>                         entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
> --
> 2.17.1
>
Reviewed-by: Steve Rutherford <srutherford@xxxxxxxxxx>