This series aims to address long-standing conflicts between dax_hmem and
CXL when handling Soft Reserved memory ranges.
Reworked from Dan's patch:
https://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl.git/patch/?id=ab70c6227ee6165a562c215d9dcb4a1c55620d5d
Previous work:
https://lore.kernel.org/all/20250715180407.47426-1-Smita.KoralahalliChannabasappa@amd.com/
Link to v2:
https://lore.kernel.org/all/20250930042814.213912-1-Smita.KoralahalliChannabasappa@amd.com/
To note:
I have dropped 6/6th patch from v1 based on discussion with Zhijian. This
patch series doesn't cover the case of DEV_DAX_HMEM=y and CXL=m, which
results in DEV_DAX_CXL being disabled.
In that configuration, ownership of the soft-reserved ranges is handled by
HMEM instead of being managed by CXL.
/proc/iomem for this case looks like below:
850000000-284fffffff : CXL Window 0
850000000-284fffffff : region3
850000000-284fffffff : Soft Reserved
850000000-284fffffff : dax0.0
850000000-284fffffff : System RAM (kmem)
2850000000-484fffffff : CXL Window 1
2850000000-484fffffff : region4
2850000000-484fffffff : Soft Reserved
2850000000-484fffffff : dax1.0
2850000000-484fffffff : System RAM (kmem)
4850000000-684fffffff : CXL Window 2
4850000000-684fffffff : region5
4850000000-684fffffff : Soft Reserved
4850000000-684fffffff : dax2.0
4850000000-684fffffff : System RAM (kmem)
Link to the patch and discussions on this:
https://lore.kernel.org/all/20250822034202.26896-7-Smita.KoralahalliChannabasappa@amd.com/
I would appreciate input on how best to handle this scenario efficiently.
Applies to mainline master.
v3 updates:
- Fixed two "From".
v2 updates:
- Removed conditional check on CONFIG_EFI_SOFT_RESERVE as dax_hmem
depends on CONFIG_EFI_SOFT_RESERVE. (Zhijian)
- Added TODO note. (Zhijian)
- Included region_intersects_soft_reserve() inside CONFIG_EFI_SOFT_RESERVE
conditional check. (Zhijian)
- insert_resource_late() -> insert_resource_expand_to_fit() and
__insert_resource_expand_to_fit() replacement. (Boris)
- Fixed Co-developed and Signed-off by. (Dan)
- Combined 2/6 and 3/6 into a single patch. (Zhijian).
- Skip local variable in remove_soft_reserved. (Jonathan)
- Drop kfree with __free(). (Jonathan)
- return 0 -> return dev_add_action_or_reset(host...) (Jonathan)
- Dropped 6/6.
- Reviewed-by tags (Dave, Jonathan)
Dan Williams (4):
dax/hmem, e820, resource: Defer Soft Reserved registration until hmem
is ready
dax/hmem: Request cxl_acpi and cxl_pci before walking Soft Reserved
ranges
dax/hmem: Use DEV_DAX_CXL instead of CXL_REGION for deferral
dax/hmem: Defer Soft Reserved overlap handling until CXL region
assembly completes
Smita Koralahalli (1):
dax/hmem: Reintroduce Soft Reserved ranges back into the iomem tree
arch/x86/kernel/e820.c | 2 +-
drivers/cxl/acpi.c | 2 +-
drivers/dax/Kconfig | 2 +
drivers/dax/hmem/device.c | 4 +-
drivers/dax/hmem/hmem.c | 128 ++++++++++++++++++++++++++++++++++----
include/linux/ioport.h | 13 +++-
kernel/resource.c | 92 +++++++++++++++++++++++----
7 files changed, 213 insertions(+), 30 deletions(-)
--
2.17.1