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Tue, 12 Jan 2021 22:54:37 +0000 (GMT) Received: from oc6034535106.ibm.com (unknown [9.211.156.88]) by b03ledav001.gho.boulder.ibm.com (Postfix) with ESMTP; Tue, 12 Jan 2021 22:54:37 +0000 (GMT) Subject: Re: [PATCH v4 01/21] ibmvfc: add vhost fields and defaults for MQ enablement To: Tyrel Datwyler , james.bottomley@hansenpartnership.com References: <20210111231225.105347-1-tyreld@linux.ibm.com> <20210111231225.105347-2-tyreld@linux.ibm.com> From: Brian King Message-ID: <0525bee7-433f-dcc7-9e35-e8706d6edee5@linux.vnet.ibm.com> Date: Tue, 12 Jan 2021 16:54:37 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20210111231225.105347-2-tyreld@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343, 18.0.737 definitions=2021-01-12_19:2021-01-12, 2021-01-12 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 adultscore=0 phishscore=0 impostorscore=0 mlxlogscore=999 clxscore=1011 mlxscore=0 bulkscore=0 spamscore=0 suspectscore=0 malwarescore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101120128 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: martin.petersen@oracle.com, linux-scsi@vger.kernel.org, james.smart@broadcom.com, linux-kernel@vger.kernel.org, brking@linux.ibm.com, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 1/11/21 5:12 PM, Tyrel Datwyler wrote: > Introduce several new vhost fields for managing MQ state of the adapter > as well as initial defaults for MQ enablement. > > Signed-off-by: Tyrel Datwyler > --- > drivers/scsi/ibmvscsi/ibmvfc.c | 8 ++++++++ > drivers/scsi/ibmvscsi/ibmvfc.h | 9 +++++++++ > 2 files changed, 17 insertions(+) > > diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c > index ba95438a8912..9200fe49c57e 100644 > --- a/drivers/scsi/ibmvscsi/ibmvfc.c > +++ b/drivers/scsi/ibmvscsi/ibmvfc.c > @@ -3302,6 +3302,7 @@ static struct scsi_host_template driver_template = { > .max_sectors = IBMVFC_MAX_SECTORS, > .shost_attrs = ibmvfc_attrs, > .track_queue_depth = 1, > + .host_tagset = 1, This doesn't seem right. You are setting host_tagset, which means you want a shared, host wide, tag set for commands. It also means that the total queue depth for the host is can_queue. However, it looks like you are allocating max_requests events for each sub crq, which means you are over allocating memory. Looking at this closer, we might have bigger problems. There is a host wide max number of commands that the VFC host supports, which gets returned on NPIV Login. This value can change across a live migration event. The ibmvfc driver, which does the same thing the lpfc driver does, modifies can_queue on the scsi_host *after* the tag set has been allocated. This looks to be a concern with ibmvfc, not sure about lpfc, as it doesn't look like we look at can_queue once the tag set is setup, and I'm not seeing a good way to dynamically change the host queue depth once the tag set is setup. Unless I'm missing something, our best options appear to either be to implement our own host wide busy reference counting, which doesn't sound very good, or we need to add some API to block / scsi that allows us to dynamically change can_queue. Thanks, Brian -- Brian King Power Linux I/O IBM Linux Technology Center