linux-kernel - Re: [PATCH v4 10/14] KVM: s390: pv: usage counter instead of flag

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Date:   Thu, 26 Aug 2021 09:58:17 +0200
From:   Janis Schoetterl-Glausch <scgl@...ux.vnet.ibm.com>
To:     Claudio Imbrenda <imbrenda@...ux.ibm.com>, kvm@...r.kernel.org
Cc:     cohuck@...hat.com, borntraeger@...ibm.com, frankja@...ux.ibm.com,
        thuth@...hat.com, pasic@...ux.ibm.com, david@...hat.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ulrich.Weigand@...ibm.com
Subject: Re: [PATCH v4 10/14] KVM: s390: pv: usage counter instead of flag

Am 18.08.21 um 15:26 schrieb Claudio Imbrenda:
> Use the is_protected field as a counter instead of a flag. This will
> be used in upcoming patches.

Maybe it should also be renamed to reflect that?
> 
> Increment the counter when a secure configuration is created, and
> decrement it when it is destroyed. Previously the flag was set when the
> set secure parameters UVC was performed.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
> Acked-by: Janosch Frank <frankja@...ux.ibm.com>
> ---
>  arch/s390/kvm/pv.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index 47db80003ea0..ee11ff6afc4f 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
> @@ -173,7 +173,8 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
>  	cc = uv_cmd_nodata(kvm_s390_pv_get_handle(kvm),
>  			   UVC_CMD_DESTROY_SEC_CONF, rc, rrc);
>  	WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
> -	atomic_set(&kvm->mm->context.is_protected, 0);
> +	if (!cc)
> +		atomic_dec(&kvm->mm->context.is_protected);
>  	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM: rc %x rrc %x", *rc, *rrc);
>  	WARN_ONCE(cc, "protvirt destroy vm failed rc %x rrc %x", *rc, *rrc);
>  	/* Intended memory leak on "impossible" error */
> @@ -214,11 +215,14 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
>  	/* Outputs */
>  	kvm->arch.pv.handle = uvcb.guest_handle;
> 
> +	atomic_inc(&kvm->mm->context.is_protected);
>  	if (cc) {
> -		if (uvcb.header.rc & UVC_RC_NEED_DESTROY)
> +		if (uvcb.header.rc & UVC_RC_NEED_DESTROY) {
>  			kvm_s390_pv_deinit_vm(kvm, &dummy, &dummy);
> -		else
> +		} else {
> +			atomic_dec(&kvm->mm->context.is_protected);
>  			kvm_s390_pv_dealloc_vm(kvm);
> +		}
>  		return -EIO;
>  	}
>  	kvm->arch.gmap->guest_handle = uvcb.guest_handle;
> @@ -241,8 +245,6 @@ int kvm_s390_pv_set_sec_parms(struct kvm *kvm, void *hdr, u64 length, u16 *rc,
>  	*rrc = uvcb.header.rrc;
>  	KVM_UV_EVENT(kvm, 3, "PROTVIRT VM SET PARMS: rc %x rrc %x",
>  		     *rc, *rrc);
> -	if (!cc)
> -		atomic_set(&kvm->mm->context.is_protected, 1);
>  	return cc ? -EINVAL : 0;
>  }
>