| From: |
| Smita Koralahalli <Smita.KoralahalliChannabasappa-AT-amd.com> |
| To: |
| <linux-cxl-AT-vger.kernel.org>, <linux-kernel-AT-vger.kernel.org>, <nvdimm-AT-lists.linux.dev>, <linux-fsdevel-AT-vger.kernel.org>, <linux-pm-AT-vger.kernel.org> |
| Subject: |
| [PATCH v2 0/5] dax/hmem, cxl: Coordinate Soft Reserved handling with CXL |
| Date: |
| Tue, 30 Sep 2025 04:28:09 +0000 |
| Message-ID: |
| <20250930042814.213912-1-Smita.KoralahalliChannabasappa@amd.com> |
| Cc: |
| Davidlohr Bueso <dave-AT-stgolabs.net>, Jonathan Cameron <jonathan.cameron-AT-huawei.com>, Dave Jiang <dave.jiang-AT-intel.com>, "Alison Schofield" <alison.schofield-AT-intel.com>, Vishal Verma <vishal.l.verma-AT-intel.com>, Ira Weiny <ira.weiny-AT-intel.com>, Dan Williams <dan.j.williams-AT-intel.com>, Matthew Wilcox <willy-AT-infradead.org>, Jan Kara <jack-AT-suse.cz>, "Rafael J . Wysocki" <rafael-AT-kernel.org>, Len Brown <len.brown-AT-intel.com>, Pavel Machek <pavel-AT-kernel.org>, Li Ming <ming.li-AT-zohomail.com>, Jeff Johnson <jeff.johnson-AT-oss.qualcomm.com>, "Ying Huang" <huang.ying.caritas-AT-gmail.com>, Yao Xingtao <yaoxt.fnst-AT-fujitsu.com>, Peter Zijlstra <peterz-AT-infradead.org>, Greg KH <gregkh-AT-linuxfoundation.org>, Nathan Fontenot <nathan.fontenot-AT-amd.com>, Smita Koralahalli <Smita.KoralahalliChannabasappa-AT-amd.com>, Terry Bowman <terry.bowman-AT-amd.com>, Robert Richter <rrichter-AT-amd.com>, Benjamin Cheatham <benjamin.cheatham-AT-amd.com>, Zhijian Li <lizhijian-AT-fujitsu.com>, "Borislav Petkov" <bp-AT-alien8.de>, Ard Biesheuvel <ardb-AT-kernel.org> |
| Archive-link: |
| Article |
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.g...
Previous work:
https://lore.kernel.org/all/20250715180407.47426-1-Smita....
Link to v1:
https://lore.kernel.org/all/20250822034202.26896-1-Smita....
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....
I would appreciate input on how best to handle this scenario efficiently.
Applies to mainline master.
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
