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

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Date:   Wed, 20 Oct 2021 16:43:44 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Peter Gonda <pgonda@...gle.com>
Cc:     kvm list <kvm@...r.kernel.org>, 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>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/5 V10] KVM: SEV: Add support for SEV-ES intra host
 migration

On 10/20/21 3:43 PM, Peter Gonda wrote:
> On Fri, Oct 15, 2021 at 3:36 PM Tom Lendacky <thomas.lendacky@....com> wrote:
>>
>> 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?
> 
> Oops, making that an easy memset was one of the pros of the |sev_es|
> refactor. Will fix and add newline in V11.

And totally up to you, but I think you can replace the memcpy() above with 
a direct assignment, if you want:

	dst_svm->sev_es = src_svm->sev_es;

Thanks,
Tom

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