Re: [Xen-devel] [PATCH v5 9/9] xen/pciback: Implement PCI reset slot or bus with 'do_flr' SysFS attribute

From: Sander Eikelenboom
Date: Thu Dec 04 2014 - 08:16:53 EST

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@xxxxxxxxxx> 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.)

So it's the ordering and skipping of the other resets that seems to make
this workaround necessary in the first place.

> David

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at