Re: [PATCH 2/4 V9] KVM: SEV: Add support for SEV-ES intra host migration

[Tom Lendacky <thomas.lendacky@amd.com>]

On 10/5/21 9:13 AM, Peter Gonda wrote:
> For SEV-ES to work with intra host migration the VMSAs, GHCB metadata,
> and other SEV-ES info needs to be preserved along with the guest's
> memory.
> 
> Signed-off-by: Peter Gonda <pgonda@google.com>
> Reviewed-by: Marc Orr <marcorr@google.com>
> Cc: Marc Orr <marcorr@google.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
> Cc: Wanpeng Li <wanpengli@tencent.com>
> Cc: Jim Mattson <jmattson@google.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> ---
>   arch/x86/kvm/svm/sev.c | 53 +++++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 52 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 6fc1935b52ea..321b55654f36 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1576,6 +1576,51 @@ static void sev_migrate_from(struct kvm_sev_info *dst,
>   	list_replace_init(&src->regions_list, &dst->regions_list);
>   }
>   
> +static int sev_es_migrate_from(struct kvm *dst, struct kvm *src)
> +{
> +	int i;
> +	struct kvm_vcpu *dst_vcpu, *src_vcpu;
> +	struct vcpu_svm *dst_svm, *src_svm;
> +
> +	if (atomic_read(&src->online_vcpus) != atomic_read(&dst->online_vcpus))
> +		return -EINVAL;
> +
> +	kvm_for_each_vcpu(i, src_vcpu, src) {
> +		if (!src_vcpu->arch.guest_state_protected)
> +			return -EINVAL;
> +	}
> +
> +	kvm_for_each_vcpu(i, src_vcpu, src) {
> +		src_svm = to_svm(src_vcpu);
> +		dst_vcpu = dst->vcpus[i];
> +		dst_vcpu = kvm_get_vcpu(dst, i);

One of these assignments of dst_vcpu can be deleted.

> +		dst_svm = to_svm(dst_vcpu);
> +
> +		/*
> +		 * Transfer VMSA and GHCB state to the destination.  Nullify and
> +		 * clear source fields as appropriate, the state now belongs to
> +		 * the destination.
> +		 */
> +		dst_vcpu->vcpu_id = src_vcpu->vcpu_id;
> +		dst_svm->vmsa = src_svm->vmsa;
> +		src_svm->vmsa = NULL;
> +		dst_svm->ghcb = src_svm->ghcb;
> +		src_svm->ghcb = NULL;
> +		dst_svm->vmcb->control.ghcb_gpa = src_svm->vmcb->control.ghcb_gpa;
> +		dst_svm->ghcb_sa = src_svm->ghcb_sa;
> +		src_svm->ghcb_sa = NULL;
> +		dst_svm->ghcb_sa_len = src_svm->ghcb_sa_len;
> +		src_svm->ghcb_sa_len = 0;
> +		dst_svm->ghcb_sa_sync = src_svm->ghcb_sa_sync;
> +		src_svm->ghcb_sa_sync = false;
> +		dst_svm->ghcb_sa_free = src_svm->ghcb_sa_free;
> +		src_svm->ghcb_sa_free = false;

Would it make sense to have a pre-patch that puts these fields into a 
struct? Then you can just copy the struct and zero it after. If anything 
is ever added for any reason, then it could/should be added to the struct 
and this code wouldn't have to change. It might be more churn than it's 
worth, just a thought.

Thanks,
Tom

> +	}
> +	to_kvm_svm(src)->sev_info.es_active = false;
> +
> +	return 0;
> +}
> +
>   int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd)
>   {
>   	struct kvm_sev_info *dst_sev = &to_kvm_svm(kvm)->sev_info;
> @@ -1604,7 +1649,7 @@ int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd)
>   	if (ret)
>   		goto out_fput;
>   
> -	if (!sev_guest(source_kvm) || sev_es_guest(source_kvm)) {
> +	if (!sev_guest(source_kvm)) {
>   		ret = -EINVAL;
>   		goto out_source;
>   	}
> @@ -1615,6 +1660,12 @@ int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd)
>   	if (ret)
>   		goto out_source_vcpu;
>   
> +	if (sev_es_guest(source_kvm)) {
> +		ret = sev_es_migrate_from(kvm, source_kvm);
> +		if (ret)
> +			goto out_source_vcpu;
> +	}
> +
>   	sev_migrate_from(dst_sev, &to_kvm_svm(source_kvm)->sev_info);
>   	kvm_for_each_vcpu (i, vcpu, source_kvm) {
>   		kvm_vcpu_reset(vcpu, /* init_event= */ false);
>