Messages in this thread | | | Date | Thu, 4 Dec 2014 15:14:32 +0100 | From | Sander Eikelenboom <> | Subject | Re: [Xen-devel] [PATCH v5 9/9] xen/pciback: Implement PCI reset slot or bus with 'do_flr' SysFS attribute |
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Hello Sander,
Thursday, December 4, 2014, 3:09:09 PM, you wrote:
> Thursday, December 4, 2014, 2:43:06 PM, you wrote:
>> On 04/12/14 13:10, Sander Eikelenboom wrote: >>> >>> Thursday, December 4, 2014, 1:24:47 PM, you wrote: >>> >>>> On 04/12/14 12:06, Konrad Rzeszutek Wilk wrote: >>>>> >>>>> On Dec 4, 2014 6:30 AM, David Vrabel <david.vrabel@citrix.com> wrote: >>>>>> >>>>>> On 03/12/14 21:40, Konrad Rzeszutek Wilk wrote: >>>>>>> >>>>>>> Instead of doing all this complex dance, we depend on the toolstack >>>>>>> doing the right thing. As such implement the 'do_flr' SysFS attribute >>>>>>> which 'xl' uses when a device is detached or attached from/to a guest. >>>>>>> It bypasses the need to worry about the PCI lock. >>>>>> >>>>>> No. Get pciback to add its own "reset" sysfs file (as I have repeatedly >>>>>> proposed). >>>>>> >>>>> >>>>> Which does not work as the kobj will complain (as there is already an 'reset' associated with the PCI device). >>> >>>> It is only needed if the core won't provide one. >>> >>>> +static int pcistub_try_create_reset_file(struct pci_dev *pci) >>>> +{ >>>> + struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(pci); >>>> + struct device *dev = &pci->dev; >>>> + int ret; >>>> + >>>> + /* Already have a per-function reset? */ >>>> + if (pci_probe_reset_function(pci) == 0) >>>> + return 0; >>>> + >>>> + ret = device_create_file(dev, &dev_attr_reset); >>>> + if (ret < 0) >>>> + return ret; >>> + dev_data->>created_reset_file = true; >>>> + return 0; >>>> +} >>> >>> Wouldn't the "core-reset-sysfs-file" be still wired to the end up calling >>> "pci.c:__pci_dev_reset" ? >>> >>> The problem with that function is that from my testing it seems that the >>> first option "pci_dev_specific_reset" always seems to return succes, so all the >>> other options are skipped (flr, pm, slot, bus). However the device it self is >>> not properly reset enough (perhaps the pci_dev_specific_reset is good enough for >>> none virtualization purposes and it's probably the least intrusive. For >>> virtualization however it would be nice to be sure it resets properly, or have a >>> way to force a specific reset routine.)
>> Then you need work with the maintainer for those specific devices or >> drivers to fix their specific reset function.
>> I'm not adding stuff to pciback to workaround broken quirks.
> OK that's a pretty clear message there, so if one wants to use pci and vga > passthrough one should better use KVM and vfio-pci.
> vfio-pci has: > - logic to do the try-slot-bus-reset logic > - it has quirks specific to vga passthrough Hrmm have to correct my self because the vga-pt quirks are part of the vfio-pci part in qemu.
The try-slot-bus-reset logic is part of the kernel vfio-pci driver though and they faced the same locking issue it seems:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=61cf16d8bd38c3dc52033ea75d5b1f8368514a17 http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=890ed578df82f5b7b5a874f9f2fa4f117305df5f
> implemented in from the looks of it a quite clean driver. > (the main issue with it so far was you could only seize devices based on > vendor and device id, which can be a problem when you have multiple devices. > However that was resolved recently if i am correct.)
> And neither of those will be supported by xen-pciback if i get your message > right ?
> -- > Sander
>> David
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