This is a note to let you know that I've just added the patch titled
cxl/port: Fix missing target list lock
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cxl-port-fix-missing-target-list-lock.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0fe5b3801a54f77adcb1ef9b8f59d4098b508c7c
Author: Dan Williams <dan.j.williams@xxxxxxxxx>
Date: Thu Dec 21 21:05:01 2023 -0800
cxl/port: Fix missing target list lock
[ Upstream commit 5459e186a5c9f412334321cff58d70dcb0e48a04 ]
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@xxxxxxxxx>
Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 4081052bb385..c67cc8c9d5cc 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -172,14 +172,10 @@ static ssize_t target_list_show(struct device *dev,
{
struct cxl_switch_decoder *cxlsd = to_cxl_switch_decoder(dev);
ssize_t offset;
- unsigned int seq;
int rc;
- do {
- seq = read_seqbegin(&cxlsd->target_lock);
- rc = emit_target_list(cxlsd, buf);
- } while (read_seqretry(&cxlsd->target_lock, seq));
-
+ guard(rwsem_read)(&cxl_region_rwsem);
+ rc = emit_target_list(cxlsd, buf);
if (rc < 0)
return rc;
offset = rc;
@@ -1579,7 +1575,7 @@ EXPORT_SYMBOL_NS_GPL(cxl_mem_find_port, CXL);
static int decoder_populate_targets(struct cxl_switch_decoder *cxlsd,
struct cxl_port *port, int *target_map)
{
- int i, rc = 0;
+ int i;
if (!target_map)
return 0;
@@ -1589,19 +1585,16 @@ static int decoder_populate_targets(struct cxl_switch_decoder *cxlsd,
if (xa_empty(&port->dports))
return -EINVAL;
- write_seqlock(&cxlsd->target_lock);
+ guard(rwsem_write)(&cxl_region_rwsem);
for (i = 0; i < cxlsd->cxld.interleave_ways; i++) {
struct cxl_dport *dport = find_dport(port, target_map[i]);
- if (!dport) {
- rc = -ENXIO;
- break;
- }
+ if (!dport)
+ return -ENXIO;
cxlsd->target[i] = dport;
}
- write_sequnlock(&cxlsd->target_lock);
- return rc;
+ return 0;
}
struct cxl_dport *cxl_hb_modulo(struct cxl_root_decoder *cxlrd, int pos)
@@ -1671,7 +1664,6 @@ static int cxl_switch_decoder_init(struct cxl_port *port,
return -EINVAL;
cxlsd->nr_targets = nr_targets;
- seqlock_init(&cxlsd->target_lock);
return cxl_decoder_init(port, &cxlsd->cxld);
}
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 6c6afda0e4c6..de2c250c894b 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -404,7 +404,6 @@ 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
*
@@ -416,7 +415,6 @@ struct cxl_endpoint_decoder {
*/
struct cxl_switch_decoder {
struct cxl_decoder cxld;
- seqlock_t target_lock;
int nr_targets;
struct cxl_dport *target[];
};
