Re: [BUG] cxl can not create region

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

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.  

> 
> 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