Re: Support for CXL v3.0 spec with QEMU

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Fri, 20 Oct 2023 13:38:22 -0700
Ira Weiny <ira.weiny@intel.com> wrote:

> Ravi Kanth wrote:
> > Hi Jonathan / Gregory,
> > Just wanted to touch base on below questions and if you have any
> > inputs on the same. Thanks for your help.
> > 
> > Thanks
> > Ravi
> > 
> > On Wed, Oct 18, 2023 at 4:00 PM Ravi Kanth <mvrravikanth@gmail.com> wrote:  
> > >
> > > Hi Jonathan / Gregory,
> > >
> > > 1. Do we have the support in CXL driver to read the "Device status
> > > registers" and specifically "Event status register" section 8.2.8.3
> > > and 8.2.8.3.1?  
> 
> Yes the upstream driver reads this when processing the Event interrupt
> from the device.  Then it uses the value to chose which logs to read.
> 
> See cxl_event_thread() in the kernel source.
> 
> > > 2. If an interrupt is posted by the device firmware, how will user
> > > space applications be notified ? Do we have an interface for the same
> > > in CXL driver?  
> 
> All events are reported through the trace infrastructure.
> 
> > >
> > > If the above features are already supported in CXL driver, Can you
> > > please point us to the sample code snippets to achieve the same?  
> 
> ndctl has the ability to monitor these events and example C code in there.
> 
> See .../cxl/event_trace.c in the ndctl project.[1]
> 
> [1] https://github.com/pmem/ndctl
> 
> > >
> > > Also does the switch cci function change part of the mainline?  
> 
> I'm not sure I parse this question but I'm also not super familiar with
> switch cci.  So I'll let Jonathan answer this.

Patches posted for review only at the moment - so 6.8 at earliest given timing.
https://lore.kernel.org/all/20231016125323.18318-1-Jonathan.Cameron@huawei.com/

Main change to existing handling is that a bunch of mailbox related handling is
factored out for reuse.  Otherwise, it's 'just another PCI endpoint driver'.

Jonathan

> 
> Ira
> 
> > >
> > > Thanks for your help in advance.
> > >
> > > Thanks
> > > Ravi
> > >  
> 
> [snip]
>