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Message-ID: <20141001073008.GC31859@redhat.com>
Date: Wed, 1 Oct 2014 10:30:08 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Marcel Apfelbaum <marcel.a@...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] PCI: add kernel parameter to override devid<->driver
mapping.
On Wed, Oct 01, 2014 at 10:06:46AM +0300, Marcel Apfelbaum wrote:
> 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@...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 slot 0001:02:03.4 to pci-stub use:
> > > driver[0001:02:03.4]=pci-stub
> > >
> > > Signed-off-by: Marcel Apfelbaum <marcel.a@...hat.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
>
>
Thinking more about it, how about just using strstr to search a string
of overrides? This will completely remove the artificial
DRIVER_OVERRIDE_MAP_SIZE as well.
> >
> > > + 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
>
>
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