From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: RFC: Automatically making a PCI device assignable in the config file Date: Fri, 5 Jul 2013 14:52:08 +0100 Message-ID: <51D6CF88.4010203@eu.citrix.com> References: <51D6CC76.4040906@citrix.com> <51D6CDE2.90808@eu.citrix.com> <51D6CEBE.4040101@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51D6CEBE.4040101@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andrew Cooper Cc: Ian Jackson , Ian Campbell , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 05/07/13 14:48, Andrew Cooper wrote: > On 05/07/13 14:45, George Dunlap wrote: >> On 05/07/13 14:39, Andrew Cooper wrote: >>> On 05/07/13 12:01, George Dunlap wrote: >>>> I've been doing some work to try to make driver domains easier to set >>>> up and use. At the moment, in order to pass a device through to a >>>> guest, you first need to assign it to pciback. This involves doing >>>> one of three things: >>>> * Running xl pci-assignable-add for the device >>>> * Specifying the device to be grabbed on the dom0 Linux command-line >>>> * Doing some hackery in /etc/modules.d >>>> >>>> None of these are very satisfying. What I think would be better is if >>>> there was a way to specify in the guest config file, "If device X is >>>> not assignable, try to make it assignable". That way you can have a >>>> driver domain grab the appropriate device just by running "xl create >>>> domnet"; and once we have the xendomains script up and running with >>>> xl, you can simply configure your domnet appropriately, and then put >>>> it in /etc/xen/auto, to be started automatically on boot. >>>> >>>> My initial idea was to add a parameter to the pci argument in the >>>> config file; for example: >>>> >>>> pci = ['08:04.1,permissive=1,seize=1'] >>>> >>>> The 'seize=1' would indicate that if bdf 08:04.1 is not already >>>> assignable, that xl should try to make is assignable. >>>> >>>> The problem here is that this would need to be parsed by >>>> xlu_pci_parse_bdf(), which only takes an argumen tof type >>>> libxl_device_pci. >>>> >>>> Now it seems to me that the right place to do this "seizing" is in xl, >>>> not inside libxl -- the functions for doing assignment exist already, >>>> and are simple and straightforward. But doing it in xl, but as a >>>> parameter of the "pci" setting, means changing xlu_pci_parse_bdf() to >>>> pass something else back, which begins to get awkward. >>>> >>>> So it seems to me we have a couple of options: >>>> 1. Create a new argument, "pci_seize" or something like that, which >>>> would be processed separately from pci >>>> 2. Change xlu_pci_parse_bdf to take a pointer to an extra struct, for >>>> arguments directed at xl rather than libxl >>>> 3. Add "seize" to libxl_device_pci, but have it only used by xl >>>> 4. Add "seize" to libxl_device_pci, and have libxl do the seizing. >>>> >>>> Any preference -- or any other ideas? >>>> >>>> -George >>> How about a setting in xl.conf of "auto-seize pci devices" ? That way >>> the seizing is entirely part of xl >> Auto-seizing is fairly dangerous; you could easily accidentally yank >> out the ethernet card, or even the disk that dom0 is using. I really >> think it should have to be enabled on a device-by-device basis. >> >> I suppose another option would be to be able to set, in xl.conf, a >> list of auto-seizeable devices. I don't really like that option as >> well, though. I'd rather be able to keep all the configuration in one >> place. >> >> -George > Or a slight less extreme version. > > If xl sees that it would need seize a device, it could ask "You are > trying to create a domain with device $FOO. Would you like to seize it > from dom0 ?" That won't work for driver domains, as we want it all to happen automatically when the host is booting. :-) -George