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Tue, 11 May 2021 20:10:23 +0000 (GMT) Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 94361136053; Tue, 11 May 2021 20:10:22 +0000 (GMT) Received: from oc4221205838.ibm.com (unknown [9.211.43.140]) by b03ledav002.gho.boulder.ibm.com (Postfix) with ESMTP; Tue, 11 May 2021 20:10:22 +0000 (GMT) Subject: Re: [PATCH v6 1/3] vfio-ccw: Check initialized flag in cp_init() To: Eric Farman , Cornelia Huck , Halil Pasic Cc: Jared Rossi , linux-s390@vger.kernel.org, kvm@vger.kernel.org References: <20210511195631.3995081-1-farman@linux.ibm.com> <20210511195631.3995081-2-farman@linux.ibm.com> From: Matthew Rosato Message-ID: <927149fb-ec36-ccfa-84ac-0b10ac472f84@linux.ibm.com> Date: Tue, 11 May 2021 16:10:21 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <20210511195631.3995081-2-farman@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: jPnOkXzgOsifylGROr8_jKzlqwCX0Hem X-Proofpoint-ORIG-GUID: w3slQTrCiJMoQCBW1eAS5vhyNr-1QJJv X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-05-11_04:2021-05-11,2021-05-11 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 suspectscore=0 impostorscore=0 bulkscore=0 adultscore=0 mlxlogscore=999 spamscore=0 clxscore=1011 mlxscore=0 lowpriorityscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2105110134 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 5/11/21 3:56 PM, Eric Farman wrote: > We have a really nice flag in the channel_program struct that > indicates if it had been initialized by cp_init(), and use it > as a guard in the other cp accessor routines, but not for a > duplicate call into cp_init(). The possibility of this occurring > is low, because that flow is protected by the private->io_mutex > and FSM CP_PROCESSING state. But then why bother checking it > in (for example) cp_prefetch() then? > > Let's just be consistent and check for that in cp_init() too. > > Fixes: 71189f263f8a3 ("vfio-ccw: make it safe to access channel programs") > Signed-off-by: Eric Farman > Reviewed-by: Cornelia Huck Acked-by: Matthew Rosato > --- > drivers/s390/cio/vfio_ccw_cp.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c > index b9febc581b1f..8d1b2771c1aa 100644 > --- a/drivers/s390/cio/vfio_ccw_cp.c > +++ b/drivers/s390/cio/vfio_ccw_cp.c > @@ -638,6 +638,10 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb) > static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 1); > int ret; > > + /* this is an error in the caller */ > + if (cp->initialized) > + return -EBUSY; > + > /* > * We only support prefetching the channel program. We assume all channel > * programs executed by supported guests likewise support prefetching. >