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Date:   Mon, 30 May 2022 14:05:14 +0200
From:   Claudio Imbrenda <imbrenda@linux.ibm.com>
To:     Nico Boehr <nrb@linux.ibm.com>
Cc:     kvm@vger.kernel.org, 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
Subject: Re: [PATCH v10 13/19] KVM: s390: pv: destroy the configuration
 before its memory
Message-ID: <20220530140514.74f6ea46@p-imbrenda>
In-Reply-To: <96ee2d8c2c64b4968529b78bd7ad8a042542d353.camel@linux.ibm.com>
References: <20220414080311.1084834-1-imbrenda@linux.ibm.com>
        <20220414080311.1084834-14-imbrenda@linux.ibm.com>
        <96ee2d8c2c64b4968529b78bd7ad8a042542d353.camel@linux.ibm.com>
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On Mon, 30 May 2022 09:37:37 +0200
Nico Boehr <nrb@linux.ibm.com> wrote:

> 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> =20
>=20
> Reviewed-by: Nico Boehr <nrb@linux.ibm.com>
>=20
> See one tiny thing below.
>=20
> > 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 =20
> [...]
> > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0cc =3D uv_cmd_nodata(kvm_s39=
0_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.gm=
ap->guest_handle, 0); =20
>=20
> Maybe it makes sense to also move the WRITE_ONCE up.

yes, I'll move it up, so that it is right after the UVC again