On Fri, Feb 13, 2026 at 07:47:08AM +0000, Yasunori Goto (Fujitsu) wrote: > 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/os9pr01mb12421aea8b27bf942cd0f18b190...@os9pr01mb12421.jpnprd01.prod.outlook.com/ > 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?
Maybe I'm misunderstanding Tomasz's Case 1), because this is not a work-around for a firmware issue. The CXL driver always tries to create DAX regions out of RAM regions. That happens if the CXL region is BIOS defined 'auto' region or a region requested via userspace. That is irregardless of Soft Reserved existence. Soft-Reserved is not a requirement for CXL or DAX region creation. That piece broke in an earlier rev of this patchset [1] where the calls to devm_cxl_add_dax_region(cxlr) started returning EPROBE_DEFER. I intended to point out to Smita, that behavior is restored in v6. --Alison [1] https://lore.kernel.org/linux-cxl/[email protected]/ > > Thanks, > --- > Yasunori Goto > >
