From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031834AbbKEChq (ORCPT ); Wed, 4 Nov 2015 21:37:46 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:25006 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031632AbbKEChn (ORCPT ); Wed, 4 Nov 2015 21:37:43 -0500 Date: Wed, 4 Nov 2015 21:37:25 -0500 From: Konrad Rzeszutek Wilk To: Bob Liu Cc: xen-devel@lists.xen.org, linux-kernel@vger.kernel.org, roger.pau@citrix.com, felipe.franciosi@citrix.com, axboe@fb.com, avanzini.arianna@gmail.com, rafal.mielniczuk@citrix.com, jonathan.davies@citrix.com, david.vrabel@citrix.com Subject: Re: [PATCH v4 08/10] xen/blkback: get the number of hardware queues/rings from blkfront Message-ID: <20151105023725.GB3949@x230.dumpdata.com> References: <1446438106-20171-1-git-send-email-bob.liu@oracle.com> <1446438106-20171-9-git-send-email-bob.liu@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1446438106-20171-9-git-send-email-bob.liu@oracle.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 02, 2015 at 12:21:44PM +0800, Bob Liu wrote: > Backend advertises "multi-queue-max-queues" to front, then get the negotiated s/then/so/ > number from "multi-queue-num-queues" wrote by blkfront. s/wrote/written/ > > Signed-off-by: Bob Liu > --- > drivers/block/xen-blkback/blkback.c | 11 +++++++++++ > drivers/block/xen-blkback/common.h | 1 + > drivers/block/xen-blkback/xenbus.c | 35 +++++++++++++++++++++++++++++------ > 3 files changed, 41 insertions(+), 6 deletions(-) > > diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c > index eaf7ec0..107cc4a 100644 > --- a/drivers/block/xen-blkback/blkback.c > +++ b/drivers/block/xen-blkback/blkback.c > @@ -83,6 +83,11 @@ module_param_named(max_persistent_grants, xen_blkif_max_pgrants, int, 0644); > MODULE_PARM_DESC(max_persistent_grants, > "Maximum number of grants to map persistently"); > > +unsigned int xenblk_max_queues; Do you want a default value? > +module_param_named(max_queues, xenblk_max_queues, uint, 0644); > +MODULE_PARM_DESC(max_queues, > + "Maximum number of hardware queues per virtual disk"); > + > /* > * Maximum order of pages to be used for the shared ring between front and > * backend, 4KB page granularity is used. > @@ -1478,6 +1483,12 @@ static int __init xen_blkif_init(void) > xen_blkif_max_ring_order = XENBUS_MAX_RING_PAGE_ORDER; > } > > + /* Allow as many queues as there are CPUs if user has not > + * specified a value. That should be part of the module_param actually. > + */ > + if (xenblk_max_queues == 0) > + xenblk_max_queues = num_online_cpus(); > + > rc = xen_blkif_interface_init(); > if (rc) > goto failed_init; > diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h > index 4de1326..fb28b91 100644 > --- a/drivers/block/xen-blkback/common.h > +++ b/drivers/block/xen-blkback/common.h > @@ -45,6 +45,7 @@ > #include > > extern unsigned int xen_blkif_max_ring_order; > +extern unsigned int xenblk_max_queues; > /* > * This is the maximum number of segments that would be allowed in indirect > * requests. This value will also be passed to the frontend. > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c > index ac4b458..cafbadd 100644 > --- a/drivers/block/xen-blkback/xenbus.c > +++ b/drivers/block/xen-blkback/xenbus.c > @@ -181,12 +181,6 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid) > INIT_LIST_HEAD(&blkif->persistent_purge_list); > INIT_WORK(&blkif->persistent_purge_work, xen_blkbk_unmap_purged_grants); > > - blkif->nr_rings = 1; > - if (xen_blkif_alloc_rings(blkif)) { > - kmem_cache_free(xen_blkif_cachep, blkif); > - return ERR_PTR(-ENOMEM); > - } > - > return blkif; > } > > @@ -606,6 +600,14 @@ static int xen_blkbk_probe(struct xenbus_device *dev, > goto fail; > } > > + /* Multi-queue: write how many queues are supported by the backend. */ > + err = xenbus_printf(XBT_NIL, dev->nodename, > + "multi-queue-max-queues", "%u", xenblk_max_queues); > + if (err) { > + pr_warn("Error writing multi-queue-num-queues\n"); > + goto fail; Why fail? If we can't - then we can't and won't advertise this support. We should still be able to work, right? That is how the ''max-ring-page-order' does it below. > + } > + > /* setup back pointer */ > be->blkif->be = be; > > @@ -997,6 +999,7 @@ static int connect_ring(struct backend_info *be) > char *xspath; > size_t xspathsize; > const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */ > + unsigned int requested_num_queues = 0; > > pr_debug("%s %s\n", __func__, dev->otherend); > > @@ -1024,6 +1027,26 @@ static int connect_ring(struct backend_info *be) > be->blkif->vbd.feature_gnt_persistent = pers_grants; > be->blkif->vbd.overflow_max_grants = 0; > > + /* > + * Read the number of hardware queues from frontend. > + */ > + err = xenbus_scanf(XBT_NIL, dev->otherend, "multi-queue-num-queues", "%u", &requested_num_queues); Please split this in two lines. > + if (err < 0) { > + requested_num_queues = 1; > + } else { > + if (requested_num_queues > xenblk_max_queues > + || requested_num_queues == 0) { > + /* buggy or malicious guest */ > + xenbus_dev_fatal(dev, err, > + "guest requested %u queues, exceeding the maximum of %u.", > + requested_num_queues, xenblk_max_queues); > + return -1; > + } > + } > + be->blkif->nr_rings = requested_num_queues; > + if (xen_blkif_alloc_rings(be->blkif)) > + return -ENOMEM; > + > pr_info("nr_rings:%d protocol %d (%s) %s\n", be->blkif->nr_rings, > be->blkif->blk_protocol, protocol, > pers_grants ? "persistent grants" : ""); > -- > 1.8.3.1 >