Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <560068a1e89c2ceec0d544fcc62fa3f95d390182.camel@linux.ibm.com>
Subject: Re: [PATCH v10 01/19] KVM: s390: pv: leak the topmost page table
 when destroy fails
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, 16 May 2022 09:22:09 +0200
In-Reply-To: <20220414080311.1084834-2-imbrenda@linux.ibm.com>
References: <20220414080311.1084834-1-imbrenda@linux.ibm.com>
         <20220414080311.1084834-2-imbrenda@linux.ibm.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.44.1 (3.44.1-1.fc36) 
MIME-Version: 1.0
Precedence: bulk

On Thu, 2022-04-14 at 10:02 +0200, Claudio Imbrenda wrote:

[...]
> +/**
> + * s390_replace_asce - Try to replace the current ASCE of a gmap
> with
> + * another equivalent one.
> + * @gmap the gmap
> + *
> + * If the allocation of the new top level page table fails, the ASCE
> is not
> + * replaced.
> + * In any case, the old ASCE is always removed from the list.
> Therefore the
> + * caller has to make sure to save a pointer to it beforehands,
> unless an
> + * intentional leak is intended.
> + */
> +int s390_replace_asce(struct gmap *gmap)
> +{
>=20
[...]
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0/* Set new table origin while =
preserving existing ASCE
> control bits */
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0asce =3D (gmap->asce & ~_ASCE_=
ORIGIN) | __pa(table);
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0WRITE_ONCE(gmap->asce, asce);

Can someone concurrently touch the control bits?