Re: [PATCH] docs/cxl: Add serial number for persistent-memdev

[Jonathan Cameron]

On Wed, 5 Mar 2025 18:35:40 +0800
Yuquan Wang <wangyuquan1236@phytium.com.cn> wrote:

> > 
> > On Tue, 4 Mar 2025 14:22:48 +0800
> > Yuquan Wang <wangyuquan1236@phytium.com.cn> wrote:
> >   
> > > > 
> > > > On Thu, Feb 20, 2025 at 04:12:13PM +0000, Jonathan Cameron wrote:    
> > > > > On Mon, 17 Feb 2025 19:20:39 +0800
> > > > > Yuquan Wang <wangyuquan1236@phytium.com.cn> wrote:
> > > > >     
> > > > > > Add serial number parameter in the cxl persistent examples.
> > > > > > 
> > > > > > Signed-off-by: Yuquan Wang <wangyuquan1236@phytium.com.cn>    
> > > > > Looks good.  I've queued it up on my gitlab staging tree, but
> > > > > Michael if you want to pick this one directly that's fine as well.    
> > > > 
> > > > See no reason to, I was not even CC'd.    
> > > 
> > > Hi, Michael
> > > 
> > > I'm sorry, this is my fault. I used "get_maintainer.pl" to check this
> > > patch's maintainers but it shows "No maintainers found, printing recent
> > > contributors". 
> > >   
> > I usually stage up multiple series together and send on to Michael.
> > So it was be being lazy for a minor change rather than anything much
> > that you did wrong.
> > 
> > If I get time I'll post a series with this a few other patches
> > later today.  
> > 
> > Jonathan
> >   
> Thank you!
> 
> BTW, I found a corner case in CXL numa node creation.
> 
> Condition: 
> 1) A UMA/NUMA system without SRAT, but with CEDT.CFMWS
> 2）Enable CONFIG_ACPI_NUMA
> 
> Results:
> 1) acpi_numa_init: the fake_pxm will be 0 and send to acpi_parse_cfmws()
> 2）If dynamically create cxl ram region, the cxl memory would be assigned
> to node0 rather than a new node
> 
> Confusions:
> 1) Is a numa system a requirement for CXL memory usage?

Obviously discussion has gone on elsewhere, but I'd say in general it
would be a bad idea to not have an SRAT because the moment we add CXL
it is definitely a NUMA system and we want the Generic Port entry to
allow us to get perf information.

So I wouldn't mind if we fail CXL init in this case, but maybe
it is worth papering over things.

Jonathan


> 2) Should we forbid this situation by adding fake_pxm check and returning
> error in acpi_numa_init()? 
> 3）Or we can add some kernel code to allow create these fake nodes on a
> system without SRAT?
> 
> Yuquan
> 
> 
> 
> 
> 
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