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

Ashish Kalra
2020-12-04T21:43:47Z

Hello Paolo,

On Fri, Dec 04, 2020 at 12:20:46PM +0100, Paolo Bonzini wrote:
> On 05/05/20 23:19, Ashish Kalra 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.
>
> This doesn't say what the feature is or does, and what the extensions are.
> As far as I understand bit 0 is a guest->host communication that it's
> properly handling the encryption bitmap.
>
Yes, your understanding for bit 0 is correct, the extensions are for any
future extensions related to this live migration support, such as
extensions/support for accelerated migration, etc.

> I applied patches -13, this one a bit changed as follows.

Yes, i will post a fresh series of this patch-set.

Thanks,
Ashish

>
> diff --git a/Documentation/virt/kvm/cpuid.rst
> b/Documentation/virt/kvm/cpuid.rst
> index cf62162d4be2..7d82d7da3835 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_ENCRYPTED_VM_BIT 16 guest checks this feature
> bit before
> + using the page encryption
> state
> + hypercall and encrypted VM
> + features MSR
> +
> 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..02528bc760b8 100644
> --- a/Documentation/virt/kvm/msr.rst
> +++ b/Documentation/virt/kvm/msr.rst
> @@ -376,3 +376,13 @@ 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_ENC_VM_FEATURE:
> + 0x4b564d08
> +
> + Control encrypted VM features.
> +
> +data:
> + Bit 0 tells the host that the guest is (1) or is not (0) issuing
> the
> + ``KVM_HC_PAGE_ENC_STATUS`` hypercall to keep the encrypted bitmap
> + up to date.
> diff --git a/arch/x86/include/uapi/asm/kvm_para.h
> b/arch/x86/include/uapi/asm/kvm_para.h
> index 950afebfba88..3dda6e416a70 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_ENCRYPTED_VM 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_ENC_VM_FEATURE 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_ENC_VM_BITMAP_VALID (1 << 0)
> +
> #endif /* _UAPI_ASM_X86_KVM_PARA_H */
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index fa67f498e838..0673531233da 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1478,6 +1478,17 @@ int svm_page_enc_status_hc(struct kvm *kvm, unsigned
> long gpa,
> return 0;
> }
>
> +void sev_update_enc_vm_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_ENC_VM_BITMAP_VALID)
> + sev->live_migration_enabled = true;
> +}
> +
> int svm_get_page_enc_bitmap(struct kvm *kvm,
> struct kvm_page_enc_bitmap *bmap)
> {
> @@ -1490,6 +1501,9 @@ 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 66f7014eaae2..8ac2c5b9c675 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -2766,6 +2766,9 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct
> msr_data *msr)
> svm->msr_decfg = data;
> break;
> }
> + case MSR_KVM_ENC_VM_FEATURE:
> + sev_update_enc_vm_flags(vcpu->kvm, data);
> + break;
> case MSR_IA32_APICBASE:
> if (kvm_vcpu_apicv_active(vcpu))
> avic_update_vapic_bar(to_svm(vcpu), data);
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index 287559b8c5b2..363c3f8d00b7 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -66,6 +66,7 @@ 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;
> };
> @@ -504,5 +505,6 @@ int svm_page_enc_status_hc(struct kvm *kvm, unsigned
> long gpa,
> unsigned long npages, unsigned long enc);
> int svm_get_page_enc_bitmap(struct kvm *kvm, struct kvm_page_enc_bitmap
> *bmap);
> int svm_set_page_enc_bitmap(struct kvm *kvm, struct kvm_page_enc_bitmap
> *bmap);
> +void sev_update_enc_vm_flags(struct kvm *kvm, u64 data);
>
> #endif
>
> Paolo
>