Re: [PATCH] cxl/acpi: fix CXL_ACPI=y + CXL_PMEM=m link failure

[dan.j.williams]

Song Liu wrote:
> On Thu, Mar 5, 2026 at 5:23 PM <dan.j.williams@xxxxxxxxx> wrote:
> >
> > Gregory Price wrote:
> > > Commit e7e222ad73d9 ("cxl: Move devm_cxl_add_nvdimm_bridge() to
> > > cxl_pmem.ko") moved devm_cxl_add_nvdimm_bridge() from cxl_core into
> > > cxl_pmem, creating a symbol dependency from cxl_acpi to cxl_pmem.
> > >
> > > When CXL_ACPI=y and CXL_PMEM=m, the built-in cxl_acpi attempts to
> > > link against a non-built-in cxl_pmem, which the linker cannot resolve.
> > >
> > > CXL_PMEM depends on LIBNVDIMM, so LIBNVDIMM=m constrains CXL_PMEM to
> > > at most =m.
> > >
> > > Change IS_ENABLED() to IS_REACHABLE(), which returns false when a
> > > built-in caller references a modular target, preventing the link error.
> > >
> > > The result is if the pmem/nvdimm symbols are not reachable at build
> > > time, then at runtime it will always return -ENODEV.
> > >
> > > Fixes: e7e222ad73d9 ("cxl: Move devm_cxl_add_nvdimm_bridge() to cxl_pmem.ko")
> > > Signed-off-by: Gregory Price <gourry@xxxxxxxxxx>
> > > ---
> > >  drivers/cxl/acpi.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> > > index 127537628817..7065413eda9f 100644
> > > --- a/drivers/cxl/acpi.c
> > > +++ b/drivers/cxl/acpi.c
> > > @@ -952,7 +952,7 @@ static int cxl_acpi_probe(struct platform_device *pdev)
> > >       if (rc < 0)
> > >               return rc;
> > >
> > > -     if (IS_ENABLED(CONFIG_CXL_PMEM))
> > > +     if (IS_REACHABLE(CONFIG_CXL_PMEM))
> > >               rc = device_for_each_child(&root_port->dev, root_port,
> > >                                          add_root_nvdimm_bridge);
> >
> > I think we want this conflict to be resolved at build time. The nice
> > thing about a new CONFIG_CXL_ACPI_PMEM symbol is you can check your
> > config to find out why your CXL PMEM is not working. Otherwise,
> > IS_REACHABLE() hides this subtelty.
> 
> Can we fix this with something like the following?

BTW, this is queued now:

https://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl.git/commit/?h=fixes&id=93d0fcdddc9e