cxl/port: Fix missing target list lock

cxl_port_setup_targets() modifies the ->targets[] array of a switch
decoder. target_list_show() expects to be able to emit a coherent
snapshot of that array by "holding" ->target_lock for read. The
target_lock is held for write during initialization of the ->targets[]
array, but it is not held for write during cxl_port_setup_targets().

The ->target_lock() predates the introduction of @cxl_region_rwsem. That
semaphore protects changes to host-physical-address (HPA) decode which
is precisely what writes to a switch decoder's target list affects.

Replace ->target_lock with @cxl_region_rwsem.

Now the side-effect of snapshotting a unstable view of a decoder's
target list is likely benign so the Fixes: tag is presumptive.

Fixes: 27b3f8d13830 ("cxl/region: Program target lists")
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 0 insertions, 2 deletions

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 687043ece101..62fa96f8567e 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -412,7 +412,6 @@ struct cxl_endpoint_decoder {
 /**
  * struct cxl_switch_decoder - Switch specific CXL HDM Decoder
  * @cxld: base cxl_decoder object
- * @target_lock: coordinate coherent reads of the target list
  * @nr_targets: number of elements in @target
  * @target: active ordered target list in current decoder configuration
  *
@@ -424,7 +423,6 @@ struct cxl_endpoint_decoder {
  */
 struct cxl_switch_decoder {
 	struct cxl_decoder cxld;
-	seqlock_t target_lock;
 	int nr_targets;
 	struct cxl_dport *target[];
 };