> -----Original Message----- > From: Alex Williamson [mailto:alex.williamson@xxxxxxxxxx] > Sent: Wednesday, October 22, 2014 1:33 PM > To: Marcel Apfelbaum > Cc: linux-pci@xxxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; marcel@xxxxxxxxxx; > mst@xxxxxxxxxx; Yoder Stuart-B08248 > Subject: Re: [PATCH v4] PCI: add kernel parameter to override devid<->driver mapping. > > [cc+ stuart] > > On Mon, 2014-10-20 at 17:04 +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@xxxxxxxxxx> > > 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 slots to specific drivers use: > > pci=driver[xxxx:xx:xx.x]=foo,driver[xxxx:xx:xx.x]=bar,... > > > > Signed-off-by: Marcel Apfelbaum <marcel.a@xxxxxxxxxx> > > --- > > v3 -> v4: > > - Addressed Alex Williamson's comments: > > - Modified the type of driver_override_entry's fields > > - Used PCI_DEVFN when appropriated > > - Removed redundant checks > > - Replaced BUG_ON with pr_err messages > > - Simpler command line parsing > > - Addressed Michael S. Tsirkin comments > > - removed DRIVER_OVERRIDE_NAME_LENGTH limitation > > v2 -> v3: > > - Corrected subject line > > v1 -> v2: > > - Addressed Michael S. Tsirkin comments > > - Removed 32 slots limitation > > - Better handling of memory allocation failures > > (preferred BUG_ON over error messages) > > - Addressed Alex Williamson's comments: > > - Modified commit message to show parameter usage more clear. > > - I preferred to re-use parse_args instead of manually using > > strstr in order to better comply with command line parsing > > rules. > > - I didn't use any locking when parsing the command line args > > (see parse_done usage) assuming that first call will be > > early in system boot and no race can occur. Please correct > > me if I am wrong. > > > > Notes: > > - 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 | 111 ++++++++++++++++++++++++++++++++++++ > > drivers/pci/pci.c | 2 + > > 3 files changed, 117 insertions(+) > > The driver_override feature that we're making use of here is also going > to be supported by platform devices and potentially more bustypes in the > future, so I'm concerned that making a pci specific kernel parameter is > too shortsighted. Instead we could hook on to BUS_NOTIFY_ADD_DEVICE for > bustypes that support driver_override so we can have a common interface. > Perhaps: > > driver_override=pci,0000:02:00.0=pci-stub;platform,fakename=vfio-platform > > Finding delimiters that don't conflict may be challenging. I think what you proposed works-- <bus-name>,<bus-dev>=<driver>; Think that will work for PCI, platform, and the new fsl-mc bus we are working on. > Also, can we > assume that bus-name:dev-name is unique for every bustype? It is for > pci, platform? I think that has to be the case. > It also seems like there's a question of how long should this override > last and how does the user disable it? Isn't that a general question for the "driver_overrride" mechanism? I'm forgetting if the mechanism in the kernel now has a way to disable it-- e.g. echo /dev/null > /sys/pci/devices/.../driver_override ?? So, it would last until explicitly disabled through sysfs. > I think with pci-stub.ids= > $VENDOR:$DEVICE a user can echo the IDs to the pci-stub/remove_id sysfs > entry to cancel the effect. The only option here seems to be a reboot. > Do we need a /sys/bus/pci/driver_overrides/{add_name,remove_name} for > this interface? Thanks, Thanks, Stuart ��.n��������+%������w��{.n�����{���"�)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
