linux-kernel - Re: [PATCH 07/12] KVM: SEV: move mirror status to destination of KVM_CAP_VM_MOVE_ENC_CONTEXT

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Date:   Mon, 29 Nov 2021 23:02:20 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        pgonda@...gle.com
Subject: Re: [PATCH 07/12] KVM: SEV: move mirror status to destination of
 KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM

On Mon, Nov 22, 2021, Paolo Bonzini wrote:
> Allow intra-host migration of a mirror VM; the destination VM will be
> a mirror of the same ASID as the source.
> 
> Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/svm/sev.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index dc974c1728b6..c1eb1c83401d 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1616,11 +1616,13 @@ static void sev_migrate_from(struct kvm_sev_info *dst,
>  	dst->asid = src->asid;
>  	dst->handle = src->handle;
>  	dst->pages_locked = src->pages_locked;
> +	dst->enc_context_owner = src->enc_context_owner;
>  
>  	src->asid = 0;
>  	src->active = false;
>  	src->handle = 0;
>  	src->pages_locked = 0;
> +	src->enc_context_owner = NULL;

Ah, since this is effectively transferring the kvm_put_kvm() "owner", I definitely
think a refcount on the number of mirrors is the way to go.

Reviewed-by: Sean Christopherson <seanjc@...gle.com>