linux-kernel - Re: [PATCH 3/5 V10] KVM: SEV: Add support for SEV-ES intra host migration

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Date:   Fri, 15 Oct 2021 16:36:27 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Peter Gonda <pgonda@...gle.com>, kvm@...r.kernel.org
Cc:     Marc Orr <marcorr@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5 V10] KVM: SEV: Add support for SEV-ES intra host
 migration

On 10/12/21 3:48 PM, 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@...gle.com>
> Reviewed-by: Marc Orr <marcorr@...gle.com>
> Cc: Marc Orr <marcorr@...gle.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Sean Christopherson <seanjc@...gle.com>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Dr. David Alan Gilbert <dgilbert@...hat.com>
> Cc: Brijesh Singh <brijesh.singh@....com>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
> Cc: Wanpeng Li <wanpengli@...cent.com>
> Cc: Jim Mattson <jmattson@...gle.com>
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: kvm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
>   arch/x86/kvm/svm/sev.c | 48 +++++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 47 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 42ff1ccfe1dc..a486ab08a766 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1600,6 +1600,46 @@ 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 = kvm_get_vcpu(dst, i);
> +		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;
> +		memcpy(&dst_svm->sev_es, &src_svm->sev_es,
> +		       sizeof(dst_svm->sev_es));
> +		dst_svm->vmcb->control.ghcb_gpa =
> +				src_svm->vmcb->control.ghcb_gpa;
> +		dst_svm->vmcb->control.vmsa_pa = __pa(dst_svm->sev_es.vmsa);
> +		dst_vcpu->arch.guest_state_protected = true;

Maybe just add a blank line here to separate the setting and clearing 
(only if you have to do another version).

> +		src_svm->vmcb->control.ghcb_gpa = 0;
> +		src_svm->vmcb->control.vmsa_pa = 0;
> +		src_vcpu->arch.guest_state_protected = false;

In the previous patch you were clearing some of the fields that are now in 
the vcpu_sev_es_state. Did you want to memset that to zero now?

Thanks,
Tom

> +	}
> +	to_kvm_svm(src)->sev_info.es_active = false;
> +
> +	return 0;
> +}
> +