linux-kernel - Re: [PATCH v4 1/4] KVM: SVM: Set sev->asid in sev_asid

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Date: Thu, 1 Feb 2024 10:20:02 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: Sean Christopherson <seanjc@...gle.com>,
 Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 Ashish Kalra <ashish.kalra@....com>
Subject: Re: [PATCH v4 1/4] KVM: SVM: Set sev->asid in sev_asid_new() instead
 of overloading the return

On 1/31/24 17:56, Sean Christopherson wrote:
> Explicitly set sev->asid in sev_asid_new() when a new ASID is successfully
> allocated, and return '0' to indicate success instead of overloading the
> return value to multiplex the ASID with error codes.  There is exactly one
> caller of sev_asid_new(), and sev_asid_free() already consumes sev->asid,
> i.e. returning the ASID isn't necessary for flexibility, nor does it
> provide symmetry between related APIs.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>   arch/x86/kvm/svm/sev.c | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index f760106c31f8..7c000088bca6 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -179,7 +179,8 @@ static int sev_asid_new(struct kvm_sev_info *sev)
>   
>   	mutex_unlock(&sev_bitmap_lock);
>   
> -	return asid;
> +	sev->asid = asid;
> +	return 0;
>   e_uncharge:
>   	sev_misc_cg_uncharge(sev);
>   	put_misc_cg(sev->misc_cg);
> @@ -246,7 +247,7 @@ static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
>   static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
>   {
>   	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> -	int asid, ret;
> +	int ret;
>   
>   	if (kvm->created_vcpus)
>   		return -EINVAL;
> @@ -257,10 +258,9 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
>   
>   	sev->active = true;
>   	sev->es_active = argp->id == KVM_SEV_ES_INIT;
> -	asid = sev_asid_new(sev);
> -	if (asid < 0)
> +	ret = sev_asid_new(sev);
> +	if (ret)
>   		goto e_no_asid;
> -	sev->asid = asid;
>   
>   	ret = sev_platform_init(&argp->error);
>   	if (ret)