Re: CXL Hot and Warm Reset Testing

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On 21/08/13 12:14PM, Bjorn Helgaas wrote:
> [+cc Amey (working on PCI resets), linux-pci]
>
> On Fri, Aug 13, 2021 at 05:01:32PM +0000, Vikram Sethi wrote:
> > Hi Dan,
> >
> > > -----Original Message-----
> > > From: Dan Williams <dan.j.williams@xxxxxxxxx>
> > >
> > > On Wed, Aug 11, 2021 at 9:42 AM Chris Browy <cbrowy@xxxxxxxxxxxxxxxx>
> > > wrote:
> > >
> > > /sys/bus/pci/devices/$device/reset is a method to trigger PCI
> > > device reset, but I do not expect that will ever gain CXL specific
> > > knowledge.
> > >
> > CXL reset may need some thought, specially for devices that don't
> > expose FLR but do expose CXL reset (while former does not affect
> > CXL.cache/mem, the latter wipes out CXL.cache/mem state in the
> > device and there is discoverability as to whether or not memory
> > contents can be cleared as part of CXL reset). We may need a way of
> > triggering CXL reset from userspace, and if the existing
> > /sys/bus/pci/devices/$device/reset won't have knowledge of CXL
> > reset, there still should be a prioritized order in the kernel in
> > which CXL reset is attempted before more drastic resets like SBR.
> > IIRC CXL reset can also impact all functions that use CXL.cache/mem,
> > but not legacy PCIe functions on the device which do not use
> > CXL.cache/mem (there is discoverability as to which functions are
> > not impacted by CXL reset).
> >
> > Thanks,
> > Vikram

We can add new reset method and expose it to userspace via new 'reset_method'
sysfs attribute introduced in this series
https://lore.kernel.org/linux-pci/20210805162917.3989-1-ameynarkhede03@xxxxxxxxx/

Thanks,
Amey



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