linux-kernel - Re: [PATCH 1/3] KVM, SEV: Refactor out function for unregistering encrypted regions

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Date:   Tue, 13 Jul 2021 21:40:55 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Peter Gonda <pgonda@...gle.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.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 1/3] KVM, SEV: Refactor out function for unregistering
 encrypted regions

On Mon, Jun 21, 2021, Peter Gonda wrote:
> Factor out helper function for freeing the encrypted region list.

...

>  arch/x86/kvm/svm/sev.c | 26 +++++++++++++++++---------
>  1 file changed, 17 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 46e339c84998..5af46ff6ec48 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1767,11 +1767,25 @@ int svm_vm_copy_asid_from(struct kvm *kvm, unsigned int source_fd)
>  	return ret;
>  }
>  
> +static void __unregister_region_list_locked(struct kvm *kvm,
> +					    struct list_head *mem_regions)

I don't think the underscores or the "locked" qualifier are necessary.  Unlike
__unregister_enc_region_locked(), there is no unregister_region_list() to avoid.

I'd also votes to drop "list" and instead use a plural "regions".  Without the
plural form, it's not immediately obvious that the difference is that this
helper deletes multiple regions.

Last nit, I assume these are all encrypted regions?  If so, unregister_enc_regions()
seems like the natural choice.

> +{
> +	struct enc_region *pos, *q;
> +
> +	lockdep_assert_held(&kvm->lock);

This locked (big thumbs up) is part of why I think it's a-ok to drop the "locked"
qualifier.

> +
> +	if (list_empty(mem_regions))
> +		return;
> +
> +	list_for_each_entry_safe(pos, q, mem_regions, list) {
> +		__unregister_enc_region_locked(kvm, pos);
> +		cond_resched();
> +	}
> +}