Re: [BUG] cxl can not create region

[Jonathan Cameron]

On Tue, 9 Aug 2022 17:08:25 +0100
Jonathan Cameron <Jonathan.Cameron@huawei.com> wrote:

> On Tue, 9 Aug 2022 21:07:06 +0800
> Bobo WL <lmw.bobo@gmail.com> wrote:
> 
> > Hi Jonathan
> > 
> > Thanks for your reply!
> > 
> > On Mon, Aug 8, 2022 at 8:37 PM Jonathan Cameron
> > <Jonathan.Cameron@huawei.com> wrote:  
> > >
> > > Probably not related to your problem, but there is a disconnect in QEMU /
> > > kernel assumptionsaround the presence of an HDM decoder when a HB only
> > > has a single root port. Spec allows it to be provided or not as an 
> > > implementation choice.
> > > Kernel assumes it isn't provide. Qemu assumes it is.
> > >
> > > The temporary solution is to throw in a second root port on the HB and not
> > > connect anything to it.  Longer term I may special case this so that the 
> > > particular
> > > decoder defaults to pass through settings in QEMU if there is only one 
> > > root port.
> > >    
> > 
> > You are right! After adding an extra HB in qemu, I can create a x1
> > region successfully.
> > But have some errors in Nvdimm:
> > 
> > [   74.925838] Unknown online node for memory at 0x10000000000, assuming 
> > node 0
> > [   74.925846] Unknown target node for memory at 0x10000000000, assuming 
> > node 0
> > [   74.927470] nd_region region0: nmem0: is disabled, failing probe  
> 
> Ah. I've seen this one, but not chased it down yet.  Was on my todo list to 
> chase
> down. Once I reach this state I can verify the HDM Decode is correct which is 
> what
> I've been using to test (Which wasn't true until earlier this week). 
> I'm currently testing via devmem, more for historical reasons than because it 
> makes
> that much sense anymore.  

*embarassed cough*.  We haven't fully hooked the LSA up in qemu yet.
I'd forgotten that was still on the todo list. I don't think it will
be particularly hard to do and will take a look in next few days.

Very very indirectly this error is causing a driver probe fail that means that
we hit a code path that has a rather odd looking check on NDD_LABELING.
Should not have gotten near that path though - hence the problem is actually
when we call cxl_pmem_get_config_data() and it returns an error because
we haven't fully connected up the command in QEMU.

Jonathan


> 
> > 
> > And x4 region still failed with same errors, using latest cxl/preview
> > branch don't work.
> > I have picked "Two CXL emulation fixes" patches in qemu, still not working.
> > 
> > Bob