RE: [PATCH v6 0/9] dax/hmem, cxl: Coordinate Soft Reserved handling with CXL and HMEM

[Yasunori Goto (Fujitsu)]

Hello, Alison-san,

I would like to clarify your answer a bit more.

> On Thu, Feb 12, 2026 at 03:44:15PM +0100, Tomasz Wolski wrote:
> > >
> > >FYI - I am able to confirm the dax regions are back for
> > >no-soft-reserved case, and my basic hotplug flow works with v6.
> > >
> > >-- Alison
> >
> > Hello Alison,
> >
> > I wanted to ask about this scenario.
> > Is my understanding correct that this fix is needed for cases without Soft
> Reserve and:
> > 1) CXL memory is installed in the server (no hotplug) and OS is
> > started
> > 2) CXL memory is hot-plugged after the OS starts
> > 3) Tests with cxl-test driver
>                                or QEMU

Though I can understand that cases 2) and 3) include QEMU, I'm not sure why Linux drivers must handle case 1).
In such a case, I feel that the platform vendor should modify the firmware to define EFI_MEMORY_SP.

In the past, I actually encountered another issue between our platform firmware and a Linux driver:
https://lore.kernel.org/linux-cxl/OS9PR01MB12421AEA8B27BF942CD0F18B19057A@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
In that case, I asked our firmware team to modify the firmware, and the issue was resolved.

Therefore, I would like to confirm why case 1) must be handled.
Have any actual machines already been released with such firmware?
Otherwise, is this just to prepare for a platform whose firmware cannot be fixed on the firmware side?

Thanks,
---
Yasunori Goto