Re: [PATCH] PCI: add kernel parameter to override devid<->driver mapping.

["Michael S. Tsirkin" <mst@redhat.com>]

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);


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