Re: CXL numa error on arm64 qemu virt machine

[Yuquan Wang <wangyuquan1236@phytium.com.cn>]

On Fri, May 10, 2024 at 06:16:46PM +0100, Jonathan Cameron wrote:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/jic23/cxl-staging.git/log/?h=arm-numa-fixes
> 
Thank you :)
> I've run out of time to sort out cover letters and things + just before the merge
> window is never a good time get anyone to pay attention to potentially controversial
> patches.  So for now I've thrown up a branch on kernel.org with Robert's
> series of fixes of related code (that's queued in the ACPI tree for the merge window)
> and Dan Williams (from several years ago) + my additions that 'work' (lightly tested)
> on qemu/arm64 with the generic port patches etc. 
> 
> I'll send out an RFC in a couple of weeks.  In meantime let me know if you
> run into any problems or have suggestions to improve them.
> 
> Jonathan
>
With the latest commit(d077bf9) in the 'arm-numa-fixes', the qemu virt
could create a cxl region with a new numa node (node 2) just like x86.
At this stage(the first time to create cxl region), everything works
fine.

However, if I use below commands to delete the created cxl region:

`daxctl offline-memory dax0.0`
`cxl disable-region region0`
`cxl destroy-region region0`

and then recreate it by `cxl create-region -d decoder0.0 -t ram`, the
kernel could not create the numa node2 again, and the kernel will print:

[  589.458971] Fallback order for Node 0: 0 1
[  589.459136] Fallback order for Node 1: 1 0
[  589.459175] Fallback order for Node 2: 0 1
[  589.459213] Built 2 zonelists, mobility grouping on.  Total pages: 1009890
[  589.459284] Policy zone: Normal

Meanwhile, the qemu reports that: 

"qemu-system-aarch64: virtio: bogus descriptor or out of resources"

Many thanks
Yuquan