Hi Tomasz,
On 2/20/2026 1:45 AM, Tomasz Wolski wrote:
Tested on QEMU and physical setups.
I have one question about "Soft Reserve" parent entries in iomem.
On QEMU I see parent "Soft Reserved":
a90000000-b4fffffff : Soft Reserved
a90000000-b4fffffff : CXL Window 0
a90000000-b4fffffff : dax1.0
a90000000-b4fffffff : System RAM (kmem)
While on my physical setup this is missing - not sure if this is okay?
BIOS-e820: [mem 0x0000002070000000-0x000000a06fffffff] soft reserved
2070000000-606fffffff : CXL Window 0
2070000000-606fffffff : region0
2070000000-606fffffff : dax0.0
2070000000-606fffffff : System RAM (kmem)
6070000000-a06fffffff : CXL Window 1
6070000000-a06fffffff : region1
6070000000-a06fffffff : dax1.0
6070000000-a06fffffff : System RAM (kmem)
Thanks for testing on both setups!
On QEMU: there is no region, so HMEM took ownership of the Soft Reserved
range (REGISTER path). Patch 9 then reintroduced the Soft Reserved entry
back into the iomem tree to reflect HMEM ownership.
On physical setup: CXL fully claimed both ranges, region0 and region1
assembled successfully (DROP path). Since CXL owns the memory, there's
no Soft Reserved parent to reintroduce.
Soft Reserved appears in /proc/iomem only when CXL does not fully claim
the range and HMEM takes over. Your physical setup is showing it
correctly. Maybe CXL_REGION config is false or region assembly failed on
and has cleaned up on QEMU so there aren't any regions?
Thanks,
Smita
Tested-by: Tomasz Wolski <[email protected]>
