Re: [BUG] cxl can not create region

[Jonathan Cameron via <qemu-devel@nongnu.org>]

On Thu, 11 Aug 2022 17:46:55 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> Dan Williams wrote:
> > Bobo WL wrote:  
> > > Hi Dan,
> > > 
> > > Thanks for your reply!
> > > 
> > > On Mon, Aug 8, 2022 at 11:58 PM Dan Williams <dan.j.williams@intel.com> wrote:  
> > > >
> > > > What is the output of:
> > > >
> > > >     cxl list -MDTu -d decoder0.0
> > > >
> > > > ...? It might be the case that mem1 cannot be mapped by decoder0.0, or
> > > > at least not in the specified order, or that validation check is broken.  
> > > 
> > > Command "cxl list -MDTu -d decoder0.0" output:  
> > 
> > Thanks for this, I think I know the problem, but will try some
> > experiments with cxl_test first.  
> 
> Hmm, so my cxl_test experiment unfortunately passed so I'm not
> reproducing the failure mode. This is the result of creating x4 region
> with devices directly attached to a single host-bridge:
> 
> # cxl create-region -d decoder3.5 -w 4 -m -g 256 mem{12,10,9,11} -s $((1<<30))
> {
>   "region":"region8",
>   "resource":"0xf1f0000000",
>   "size":"1024.00 MiB (1073.74 MB)",
>   "interleave_ways":4,
>   "interleave_granularity":256,
>   "decode_state":"commit",
>   "mappings":[
>     {
>       "position":3,
>       "memdev":"mem11",
>       "decoder":"decoder21.0"
>     },
>     {
>       "position":2,
>       "memdev":"mem9",
>       "decoder":"decoder19.0"
>     },
>     {
>       "position":1,
>       "memdev":"mem10",
>       "decoder":"decoder20.0"
>     },
>     {
>       "position":0,
>       "memdev":"mem12",
>       "decoder":"decoder22.0"
>     }
>   ]
> }
> cxl region: cmd_create_region: created 1 region
> 
> > Did the commit_store() crash stop reproducing with latest cxl/preview
> > branch?  
> 
> I missed the answer to this question.
> 
> All of these changes are now in Linus' tree perhaps give that a try and
> post the debug log again?

Hi Dan,

I've moved onto looking at this one.
1 HB, 2RP (to make it configure the HDM decoder in the QEMU HB, I'll tidy that up
at some stage), 1 switch, 4 downstream switch ports each with a type 3

I'm not getting a crash, but can't successfully setup a region.
Upon adding the final target
It's failing in check_last_peer() as pos < distance.
Seems distance is 4 which makes me think it's using the wrong level of the heirarchy for
some reason or that distance check is wrong.
Wasn't a good idea to just skip that step though as it goes boom - though
stack trace is not useful.

Jonathan