Hi Smita, >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 a lot for clarifying the behavior. I checked QEMU again and it works as you described (sorry, I must've mixed something up in my notes during previous test) >Thanks, >Smita > > Tested-by: Tomasz Wolski <[email protected]>
