lkml.org 
[lkml]   [2014]   [Oct]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH] PCI: add kernel parameter to override devid<->driver mapping.
    From
    Date
    On Wed, 2014-10-01 at 09:52 +0300, Michael S. Tsirkin wrote:
    > On Tue, Sep 30, 2014 at 07:38:35PM +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@redhat.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 slot 0001:02:03.4 to pci-stub use:
    > > driver[0001:02:03.4]=pci-stub
    > >
    > > Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
    > > ---
    > > Notes:
    > > - For the moment only 32 slots can be assigned specific driver.
    > > - 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 | 1 +
    > > drivers/pci/pci.c | 61 +++++++++++++++++++++++++++++++++++++
    > > drivers/pci/pci.h | 1 +
    > > 4 files changed, 67 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..7a7ed85 100644
    > > --- a/drivers/pci/bus.c
    > > +++ b/drivers/pci/bus.c
    > > @@ -245,6 +245,7 @@ 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..0a3e07c 100644
    > > --- a/drivers/pci/pci.c
    > > +++ b/drivers/pci/pci.c
    > > @@ -4426,6 +4426,65 @@ void __weak pci_fixup_cardbus(struct pci_bus *bus)
    > > }
    > > EXPORT_SYMBOL(pci_fixup_cardbus);
    > >
    > > +#define DRIVER_OVERRIDE_NAME_LENGTH 64
    > > +#define DRIVER_OVERRIDE_MAP_SIZE 32
    > > +
    > > +struct driver_override_entry {
    > > + unsigned int domain;
    > > + unsigned char bus;
    > > + unsigned int devfn;
    > > + char driver_name[DRIVER_OVERRIDE_NAME_LENGTH];
    > > +};
    > > +
    > > +static struct driver_override_entry __initdata
    > > + driver_override_map[DRIVER_OVERRIDE_MAP_SIZE];
    > > +static int driver_override_num_entries __initdata;
    > > +
    > > +void pci_device_setup_driver_override(struct pci_dev *dev)
    > > +{
    > > + int i;
    > > +
    > > + for (i = 0; i < driver_override_num_entries; i++) {
    > > + if (pci_domain_nr(dev->bus) != driver_override_map[i].domain ||
    > > + dev->bus->number != driver_override_map[i].bus ||
    > > + dev->devfn != driver_override_map[i].devfn)
    > > + continue;
    > > +
    > > + dev->driver_override = kstrndup(driver_override_map[i].driver_name,
    > > + DRIVER_OVERRIDE_NAME_LENGTH,
    > > + GFP_KERNEL);
    >
    >
    Hi,

    > You allocate this entry but never free it?
    Is being freed in pci_release_dev function.

    > Shouldn't allocation failure be handled in some way?
    I thought about it, but in my opinion there is no need for error
    handling in this situation.
    - On the worst case scenario it will load the regular driver, no harm done.
    (kstrndup will return NULL)
    - It is used in pci_bus_add_device workflow that has no error flow
    that I am aware of, and even if it were an error flow, in my opinion
    this is not enough to stop system boot.
    But thinking of this again, maybe a pr_err message?

    Your review is most appreciated.
    Thanks,
    Marcel


    >
    > > + break;
    > > + }
    > > +}
    > > +
    > > +static void __init pci_parse_driver_override(char *str)
    > > +{
    > > + unsigned int domain, bus, dev, fn;
    > > + char driver_name[DRIVER_OVERRIDE_NAME_LENGTH];
    > > + int ret, next_entry;
    > > + char format[] = "[%4x:%2x:%2x.%2x]=%%%ds";
    > > +
    > > + sprintf(format + 18, "%%%ds", DRIVER_OVERRIDE_NAME_LENGTH);
    > > + ret = sscanf(str, format, &domain, &bus, &dev, &fn, driver_name);
    > > +
    > > + if (ret != 5) {
    > > + pr_err("PCI: Invalid command line: driver%s\n", str);
    > > + return;
    > > + }
    > > +
    > > + if (driver_override_num_entries == DRIVER_OVERRIDE_MAP_SIZE) {
    > > + pr_err("PCI: Driver map overflow - ignoring driver%s\n", str);
    > > + return;
    > > + }
    > > +
    > > + next_entry = driver_override_num_entries++;
    > > + driver_override_map[next_entry].domain = domain;
    > > + driver_override_map[next_entry].bus = bus && 0xff;
    > > + driver_override_map[next_entry].devfn = ((dev & 0x1f) << 3) | (fn & 0x7);
    > > + memcpy(driver_override_map[next_entry].driver_name,
    > > + driver_name, sizeof(driver_name));
    > > +}
    > > +
    > > static int __init pci_setup(char *str)
    > > {
    > > while (str) {
    > > @@ -4468,6 +4527,8 @@ 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)) {
    > > + pci_parse_driver_override(str + 6);
    > > } else {
    > > printk(KERN_ERR "PCI: Unknown option `%s'\n",
    > > str);
    > > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
    > > index 0601890..023d78b 100644
    > > --- a/drivers/pci/pci.h
    > > +++ b/drivers/pci/pci.h
    > > @@ -197,6 +197,7 @@ enum pci_bar_type {
    > > bool pci_bus_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *pl,
    > > int crs_timeout);
    > > int pci_setup_device(struct pci_dev *dev);
    > > +void pci_device_setup_driver_override(struct pci_dev *dev);
    > > int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
    > > struct resource *res, unsigned int reg);
    > > int pci_resource_bar(struct pci_dev *dev, int resno, enum pci_bar_type *type);
    > > --
    > > 1.8.3.1





    \
     
     \ /
      Last update: 2014-10-01 09:41    [W:2.877 / U:0.060 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site