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Message-ID: <1412694831.16569.3.camel@localhost.localdomain>
Date: Tue, 07 Oct 2014 18:13:51 +0300
From: Marcel Apfelbaum <marcel.a@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: linux-pci@...r.kernel.org, bhelgaas@...gle.com,
linux-kernel@...r.kernel.org, marcel@...hat.com,
alex.williamson@...hat.com
Subject: Re: [PATCH v3] PCI: add kernel parameter to override devid<->driver
mapping.
On Tue, 2014-10-07 at 18:02 +0300, Michael S. Tsirkin wrote:
> On Tue, Oct 07, 2014 at 05:48:32PM +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 <alex.williamson@...hat.com>
> > 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 <marcel.a@...hat.com>
> > ---
> > 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 | 86 +++++++++++++++++++++++++++++++++++++
> > drivers/pci/pci.c | 2 +
> > 3 files changed, 92 insertions(+)
> >
> > 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..d2c0721 100644
> > --- a/drivers/pci/bus.c
> > +++ b/drivers/pci/bus.c
> > @@ -230,6 +230,91 @@ EXPORT_SYMBOL(pci_bus_alloc_resource);
> >
> > void __weak pcibios_resource_survey_bus(struct pci_bus *bus) { }
> >
> > +#define DRIVER_OVERRIDE_NAME_LENGTH 64
>
> Do we know all drivers have shorter names?
Hi Michael,
I saw this assumption in at least one place (sadly I don't remember where)
and I chose to follow it. It seems a reasonable one in my opinion.
Thanks,
Marcel
>
> > +
> > +struct driver_override_entry {
> > + unsigned int domain;
> > + unsigned char bus;
> > + unsigned int devfn;
> > + char driver_name[DRIVER_OVERRIDE_NAME_LENGTH];
> > + 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 driver_name[DRIVER_OVERRIDE_NAME_LENGTH];
> > + char format[] = "[%4x:%2x:%2x.%2x]=%%%ds";
> > + struct driver_override_entry *entry;
> > + int ret;
> > +
> > + while (val) {
> > + char *k = strchr(val, ',');
> > +
> > + if (k)
> > + *k++ = 0;
> > +
> > + if (strncmp(val, "driver", 6)) {
> > + val = k;
> > + continue;
> > + }
> > +
> > + sprintf(format + 18, "%%%ds", DRIVER_OVERRIDE_NAME_LENGTH);
> > + ret = sscanf(val + 6, format, &domain, &bus, &dev, &fn,
> > + driver_name);
> > + if (ret != 5) {
> > + pr_err("PCI: Invalid command line: %s\n", val);
> > + val = k;
> > + continue;
> > + }
> > +
> > + entry = kzalloc(sizeof(*entry), GFP_KERNEL);
> > + BUG_ON(!entry);
> > +
> > + INIT_LIST_HEAD(&entry->list);
> > + entry->domain = domain;
> > + entry->bus = bus && 0xff;
> > + entry->devfn = ((dev & 0x1f) << 3) | (fn & 0x7);
> > + memcpy(entry->driver_name, driver_name, sizeof(driver_name));
> > +
> > + list_add_tail(&entry->list, &driver_override_entries);
> > + val = k;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +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);
> > +
> > + BUG_ON(!cmdline);
> > +
> > + 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);
> > + BUG_ON(!dev->driver_override);
> > + break;
> > + }
> > +}
> > +
> > /**
> > * pci_bus_add_device - start driver for a single device
> > * @dev: device to add
> > @@ -245,6 +330,7 @@ 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 b7678be..6bd7844 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -4468,6 +4468,8 @@ 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);
> > --
> > 1.8.3.1
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