On Tue, 22 Oct 2024 18:43:24 -0700 Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > When the CXL subsystem is built-in the module init order is determined > by Makefile order. That order violates expectations. The expectation is > that cxl_acpi and cxl_mem can race to attach and that if cxl_acpi wins > the race cxl_mem will find the enabled CXL root ports it needs and if > cxl_acpi loses the race it will retrigger cxl_mem to attach via > cxl_bus_rescan(). That only works if cxl_acpi can assume ports are > enabled immediately upon cxl_acpi_probe() return. That in turn can only > happen in the CONFIG_CXL_ACPI=y case if the cxl_port object appears > before the cxl_acpi object in the Makefile. > > Fix up the order to prevent initialization failures, and make sure that > cxl_port is built-in if cxl_acpi is also built-in. > > As for what contributed to this not being found earlier, the CXL > regression environment, cxl_test, builds all CXL functionality as a > module to allow to symbol mocking and other dynamic reload tests. As a > result there is no regression coverage for the built-in case. > > Reported-by: Gregory Price <gourry@xxxxxxxxxx> > Closes: http://lore.kernel.org/20241004212504.1246-1-gourry@xxxxxxxxxx > Tested-by: Gregory Price <gourry@xxxxxxxxxx> > Fixes: 8dd2bc0f8e02 ("cxl/mem: Add the cxl_mem driver") I don't like this due to likely long term fragility, but any other solution is probably more painful. Long term we should really get a regression test for these ordering issues in place in one of the CIs. Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> > Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx> > Cc: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx> > Cc: Dave Jiang <dave.jiang@xxxxxxxxx> > Cc: Alison Schofield <alison.schofield@xxxxxxxxx> > Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx> > Cc: Ira Weiny <ira.weiny@xxxxxxxxx> > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> > --- > drivers/cxl/Kconfig | 1 + > drivers/cxl/Makefile | 20 ++++++++++++++------ > 2 files changed, 15 insertions(+), 6 deletions(-) > > diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig > index 29c192f20082..876469e23f7a 100644 > --- a/drivers/cxl/Kconfig > +++ b/drivers/cxl/Kconfig > @@ -60,6 +60,7 @@ config CXL_ACPI > default CXL_BUS > select ACPI_TABLE_LIB > select ACPI_HMAT > + select CXL_PORT > help > Enable support for host managed device memory (HDM) resources > published by a platform's ACPI CXL memory layout description. See > diff --git a/drivers/cxl/Makefile b/drivers/cxl/Makefile > index db321f48ba52..2caa90fa4bf2 100644 > --- a/drivers/cxl/Makefile > +++ b/drivers/cxl/Makefile > @@ -1,13 +1,21 @@ > # SPDX-License-Identifier: GPL-2.0 > + > +# Order is important here for the built-in case: > +# - 'core' first for fundamental init > +# - 'port' before platform root drivers like 'acpi' so that CXL-root ports > +# are immediately enabled > +# - 'mem' and 'pmem' before endpoint drivers so that memdevs are > +# immediately enabled > +# - 'pci' last, also mirrors the hardware enumeration hierarchy > obj-y += core/ > -obj-$(CONFIG_CXL_PCI) += cxl_pci.o > -obj-$(CONFIG_CXL_MEM) += cxl_mem.o > +obj-$(CONFIG_CXL_PORT) += cxl_port.o > obj-$(CONFIG_CXL_ACPI) += cxl_acpi.o > obj-$(CONFIG_CXL_PMEM) += cxl_pmem.o > -obj-$(CONFIG_CXL_PORT) += cxl_port.o > +obj-$(CONFIG_CXL_MEM) += cxl_mem.o > +obj-$(CONFIG_CXL_PCI) += cxl_pci.o > > -cxl_mem-y := mem.o > -cxl_pci-y := pci.o > +cxl_port-y := port.o > cxl_acpi-y := acpi.o > cxl_pmem-y := pmem.o security.o > -cxl_port-y := port.o > +cxl_mem-y := mem.o > +cxl_pci-y := pci.o > >
