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Message-ID: <96ee2d8c2c64b4968529b78bd7ad8a042542d353.camel@linux.ibm.com>
Subject: Re: [PATCH v10 13/19] KVM: s390: pv: destroy the configuration
 before its memory
From:   Nico Boehr <nrb@linux.ibm.com>
To:     Claudio Imbrenda <imbrenda@linux.ibm.com>, kvm@vger.kernel.org
Cc:     borntraeger@de.ibm.com, frankja@linux.ibm.com, thuth@redhat.com,
        pasic@linux.ibm.com, david@redhat.com, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org, scgl@linux.ibm.com,
        mimu@linux.ibm.com
Date:   Mon, 30 May 2022 09:37:37 +0200
In-Reply-To: <20220414080311.1084834-14-imbrenda@linux.ibm.com>
References: <20220414080311.1084834-1-imbrenda@linux.ibm.com>
         <20220414080311.1084834-14-imbrenda@linux.ibm.com>
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On Thu, 2022-04-14 at 10:03 +0200, Claudio Imbrenda wrote:
> Move the Destroy Secure Configuration UVC before the loop to destroy
> the memory. If the protected VM has memory, it will be cleaned up and
> made accessible by the Destroy Secure Configuraion UVC. The struct
> page for the relevant pages will still have the protected bit set, so
> the loop is still needed to clean that up.
>=20
> Switching the order of those two operations does not change the
> outcome, but it is significantly faster.
>=20
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

Reviewed-by: Nico Boehr <nrb@linux.ibm.com>

See one tiny thing below.

> diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
> index be3b467f8feb..bd850be08c86 100644
> --- a/arch/s390/kvm/pv.c
> +++ b/arch/s390/kvm/pv.c
[...]
> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0cc =3D uv_cmd_nodata(kvm_s390_=
pv_get_handle(kvm),
> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0 UVC_CMD_DESTROY_SEC_CONF, rc, rrc);
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0WRITE_ONCE(kvm->arch.gmap=
->guest_handle, 0);

Maybe it makes sense to also move the WRITE_ONCE up.