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Re: [Xen-devel] Device Reset on Nvidia GPUs

On Fri, Nov 15, 2013 at 02:29:39PM +0000, Gordan Bobic wrote:
> On Fri, 15 Nov 2013 14:27:21 +0000, Stefano Stabellini
> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> >On Fri, 15 Nov 2013, Gordan Bobic wrote:
> >>I've noticed that nouveau driver has a sysfs reset implemented
> >>(although I'm not sure whether it is just a stub or whether it
> >>does anything).
> >>
> >>Now, I fully understand that this is not actually necessary,
> >>based purely on empirical evidence:
> >>
> >>My ATI cards reliably crash the host when the domU the are passed
> >>to is rebooted, and the xen-pciback driver does have the sysfs
> >>reset implemented for ATI cards.
> >>
> >>OTOH, my (modified) Nvidia cards handle domU reboots perfectly
> >>and the xen-pciback driver has no sysfs reset implementation
> >>for those.
> >>
> >>So I'm kind of torn between:
> >>1) It's not broken so don't even think about trying to fix it.
> >>2) Since FOSS reset implementation seems to exist, it might be
> >>handy to port it into the xen-pciback feature list (caveat:
> >>this may impact 1), which would be embarrasing).
> >>
> >>Thoughts?
> >
> >libxl is capable of using the sysfs reset node, so there shouldn't be
> >any needed for porting the reset code to pciback
> Not quite - when the device is owned by xen-pciback, there is
> no reset node. When it is owned by nouveau, the reset node in
> sysfs is there.

Sure, but pciback does the reset:

      /* We need the device active to save the state. */                      
        dev_dbg(&dev->dev, "save state of device\n");                           
        dev_data->pci_saved_state = pci_store_saved_state(dev);                 
        if (!dev_data->pci_saved_state)                                         
                dev_err(&dev->dev, "Could not store PCI conf saved state!\n");  
        else {                                                                  
                dev_dbg(&dev->dev, "resetting (FLR, D3, etc) the device\n");    

The pci_reset_function(..) - the non-locked variant) is called when you
do 'reset' to the SysFS.

Unless the nouveau driver does some extra 'reset'?
> Gordan
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