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Date: Wed, 1 Oct 2014 09:52:27 +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 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);
You allocate this entry but never free it?
Shouldn't allocation failure be handled in some way?
> + 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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