6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Dave Jiang <dave.jiang@xxxxxxxxx>
commit 36a1c2ee50f573972aea3c3019555f47ee0094c0 upstream.
The new helper "cxl_num_decoders_committed()" added a lockdep assertion
to validate that port->commit_end is protected against modification.
That assertion fires in init_hdm_decoder() where it is initializing
port->commit_end. Given that it is both accessing and writing that
property it obstensibly needs the lock.
In practice, CXL decoder commit rules (must commit in order) and the
in-order discovery of device decoders makes the manipulation of
->commit_end in init_hdm_decoder() safe. However, rather than rely on
the subtle rules of CXL hardware, just make the implementation obviously
correct from a software perspective.
The Fixes: tag is only for cleaning up a lockdep splat, there is no
functional issue addressed by this fix.
Fixes: 458ba8189cb4 ("cxl: Add cxl_decoders_committed() helper")
Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Link: https://lore.kernel.org/r/170025232811.2147250.16376901801315194121.stgit@djiang5-mobl3
Acked-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/cxl/core/hdm.c | 2 ++
1 file changed, 2 insertions(+)
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -848,6 +848,8 @@ static int init_hdm_decoder(struct cxl_p
cxld->target_type = CXL_DECODER_HOSTONLYMEM;
else
cxld->target_type = CXL_DECODER_DEVMEM;
+
+ guard(rwsem_write)(&cxl_region_rwsem);
if (cxld->id != cxl_num_decoders_committed(port)) {
dev_warn(&port->dev,
"decoder%d.%d: Committed out of order\n",
