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Date: Wed, 01 Oct 2014 10:06:46 +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] PCI: add kernel parameter to override devid<->driver
mapping.
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
>
> > + 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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