Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932114AbaJVSct (ORCPT ); Wed, 22 Oct 2014 14:32:49 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40463 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754657AbaJVScr (ORCPT ); Wed, 22 Oct 2014 14:32:47 -0400 Message-ID: <1414002755.4202.253.camel@ul30vt.home> Subject: Re: [PATCH v4] PCI: add kernel parameter to override devid<->driver mapping. From: Alex Williamson To: Marcel Apfelbaum Cc: linux-pci@vger.kernel.org, bhelgaas@google.com, linux-kernel@vger.kernel.org, marcel@redhat.com, mst@redhat.com, Stuart Yoder Date: Wed, 22 Oct 2014 12:32:35 -0600 In-Reply-To: <1413813882-27047-1-git-send-email-marcel.a@redhat.com> References: <1413813882-27047-1-git-send-email-marcel.a@redhat.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [cc+ stuart] On Mon, 2014-10-20 at 17:04 +0300, Marcel Apfelbaum wrote: > Scanning a lot of devices during boot requires a lot of time. > On other scenarios there is a need to bind a driver to a specific slot. > > Binding devices to pci-stub driver does not work, > as it will not differentiate between devices of the > same type. Using some start scripts is error prone. > > The solution leverages driver_override functionality introduced by > > commit: 782a985d7af26db39e86070d28f987cad21313c0 > Author: Alex Williamson > Date: Tue May 20 08:53:21 2014 -0600 > > PCI: Introduce new device binding path using pci_dev.driver_override > > In order to bind PCI slots to specific drivers use: > pci=driver[xxxx:xx:xx.x]=foo,driver[xxxx:xx:xx.x]=bar,... > > Signed-off-by: Marcel Apfelbaum > --- > v3 -> v4: > - Addressed Alex Williamson's comments: > - Modified the type of driver_override_entry's fields > - Used PCI_DEVFN when appropriated > - Removed redundant checks > - Replaced BUG_ON with pr_err messages > - Simpler command line parsing > - Addressed Michael S. Tsirkin comments > - removed DRIVER_OVERRIDE_NAME_LENGTH limitation > v2 -> v3: > - Corrected subject line > v1 -> v2: > - Addressed Michael S. Tsirkin comments > - Removed 32 slots limitation > - Better handling of memory allocation failures > (preferred BUG_ON over error messages) > - Addressed Alex Williamson's comments: > - Modified commit message to show parameter usage more clear. > - I preferred to re-use parse_args instead of manually using > strstr in order to better comply with command line parsing > rules. > - I didn't use any locking when parsing the command line args > (see parse_done usage) assuming that first call will be > early in system boot and no race can occur. Please correct > me if I am wrong. > > Notes: > - I have further ideas on top of this patch based on your reviews. > I thought of: > - Use wildcards to specify entire buses/devices, something like: > driver[0001:02:*.*]=pci-stub > - Use comma to separate several devices: > driver[0001:02:03.4,0001:02:04.0,...]=pci-stub > - Make domain optional: > driver[00:03.0]=pci-stub > > Comments will be appreciated, > Thanks, > Marcel > Documentation/kernel-parameters.txt | 4 ++ > drivers/pci/bus.c | 111 ++++++++++++++++++++++++++++++++++++ > drivers/pci/pci.c | 2 + > 3 files changed, 117 insertions(+) The driver_override feature that we're making use of here is also going to be supported by platform devices and potentially more bustypes in the future, so I'm concerned that making a pci specific kernel parameter is too shortsighted. Instead we could hook on to BUS_NOTIFY_ADD_DEVICE for bustypes that support driver_override so we can have a common interface. Perhaps: driver_override=pci,0000:02:00.0=pci-stub;platform,fakename=vfio-platform Finding delimiters that don't conflict may be challenging. Also, can we assume that bus-name:dev-name is unique for every bustype? It is for pci, platform? It also seems like there's a question of how long should this override last and how does the user disable it? I think with pci-stub.ids= $VENDOR:$DEVICE a user can echo the IDs to the pci-stub/remove_id sysfs entry to cancel the effect. The only option here seems to be a reboot. Do we need a /sys/bus/pci/driver_overrides/{add_name,remove_name} for this interface? Thanks, Alex > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > index 5ae8608..c1cbb4c 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -2631,6 +2631,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > pcie_scan_all Scan all possible PCIe devices. Otherwise we > only look for one device below a PCIe downstream > port. > + driver Provide an override to the devid<->driver mapping > + for a specific slot. > + Bind PCI slot 0001:02:03.4 to pci-stub by: > + driver[0001:02:03.4]=pci-stub > > pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power > Management. > diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c > index 73aef51..b49f5cc 100644 > --- a/drivers/pci/bus.c > +++ b/drivers/pci/bus.c > @@ -15,6 +15,8 @@ > #include > #include > > +#include > + > #include "pci.h" > > void pci_add_resource_offset(struct list_head *resources, struct resource *res, > @@ -230,6 +232,114 @@ EXPORT_SYMBOL(pci_bus_alloc_resource); > > void __weak pcibios_resource_survey_bus(struct pci_bus *bus) { } > > +struct driver_override_entry { > + u16 domain; > + u8 bus; > + u8 devfn; > + char *driver_name; > + struct list_head list; > +}; > + > +static LIST_HEAD(driver_override_entries); > + > +static int pci_device_parse_driver_override(char *param, char *val, > + const char *unused) > +{ > + unsigned int domain, bus, dev, fn; > + char *buf; > + struct driver_override_entry *entry; > + int ret; > + > + buf = kmalloc(COMMAND_LINE_SIZE, GFP_KERNEL); > + if (!buf) > + goto err_buf; > + > + while (val) { > + char *k = strchr(val, ','); > + > + if (k) > + *k++ = 0; > + > + if (strncmp(val, "driver", 6)) { > + val = k; > + continue; > + } > + > + memset(buf, 0, COMMAND_LINE_SIZE); > + ret = sscanf(val + 6, "[%4x:%2x:%2x.%2x]=%s", > + &domain, &bus, &dev, &fn, buf); > + if (ret != 5) { > + pr_warn("PCI: Invalid command line: %s\n", val); > + val = k; > + continue; > + } > + > + entry = kzalloc(sizeof(*entry), GFP_KERNEL); > + if (!entry) > + goto err_entry; > + > + INIT_LIST_HEAD(&entry->list); > + entry->domain = domain; > + entry->bus = bus; > + entry->devfn = PCI_DEVFN(dev, fn); > + entry->driver_name = kstrdup(buf, GFP_KERNEL); > + if (!entry->driver_name) > + goto err_driver_name; > + > + list_add_tail(&entry->list, &driver_override_entries); > + val = k; > + } > + > + kfree(buf); > + return 0; > + > +err_driver_name: > + kfree(entry); > + > +err_entry: > + kfree(buf); > + > +err_buf: > + pr_err("PCI: Out of memory while parsing command line: %s\n", val); > + return -ENOMEM; > +} > + > +static void pci_device_setup_driver_override(struct pci_dev *dev) > +{ > + static int parse_done; > + struct driver_override_entry *entry; > + > + if (!parse_done) { > + char *cmdline = kstrdup(saved_command_line, GFP_KERNEL); > + > + if (!cmdline) > + goto err_out_of_mem; > + > + parse_args("pci", cmdline, NULL, > + 0, 0, 0, &pci_device_parse_driver_override); > + kfree(cmdline); > + parse_done = 1; > + } > + > + list_for_each_entry(entry, &driver_override_entries, list) { > + if (pci_domain_nr(dev->bus) != entry->domain || > + dev->bus->number != entry->bus || > + dev->devfn != entry->devfn) > + continue; > + > + dev->driver_override = kstrdup(entry->driver_name, GFP_KERNEL); > + if (!dev->driver_override) > + goto err_out_of_mem; > + > + break; > + } > + > + return; > + > +err_out_of_mem: > + pr_err("PCI: Out of memory while setting up driver override\n"); > +} > + > /** > * pci_bus_add_device - start driver for a single device > * @dev: device to add > @@ -245,6 +355,7 @@ void pci_bus_add_device(struct pci_dev *dev) > * are not assigned yet for some devices. > */ > pci_fixup_device(pci_fixup_final, dev); > + pci_device_setup_driver_override(dev); > pci_create_sysfs_dev_files(dev); > pci_proc_attach_device(dev); > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index 625a4ac..37809d4 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -4508,6 +4508,8 @@ static int __init pci_setup(char *str) > pcie_bus_config = PCIE_BUS_PEER2PEER; > } else if (!strncmp(str, "pcie_scan_all", 13)) { > pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS); > + } else if (!strncmp(str, "driver", 6)) { > + /* lazy evaluation by the pci subsystem */ > } else { > printk(KERN_ERR "PCI: Unknown option `%s'\n", > str); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/