From: Huang Ying <ying.huang@intel.com>
Date: Fri, 8 Dec 2023 03:06:36 +0000 (+0800)
Subject: cxl/port: Fix decoder initialization when nr_targets > interleave_ways
X-Git-Tag: v6.8-rc1~46^2~2^2~1
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d6488fee66472b468ed88d265b14aa3f04dc3bdf;p=thirdparty%2Flinux.git

cxl/port: Fix decoder initialization when nr_targets > interleave_ways

The decoder_populate_targets() helper walks all of the targets in a port
and makes sure they can be looked up in @target_map. Where @target_map
is a lookup table from target position to target id (corresponding to a
cxl_dport instance). However @target_map is only responsible for
conveying the active dport instances as indicated by interleave_ways.

When nr_targets > interleave_ways it results in
decoder_populate_targets() walking off the end of the valid entries in
@target_map. Given target_map is initialized to 0 it results in the
dport lookup failing if position 0 is not mapped to a dport with an id
of 0:

  cxl_port port3: Failed to populate active decoder targets
  cxl_port port3: Failed to add decoder
  cxl_port port3: Failed to add decoder3.0
  cxl_bus_probe: cxl_port port3: probe: -6

This bug also highlights that when the decoder's ->targets[] array is
written in cxl_port_setup_targets() it is missing a hold of the
targets_lock to synchronize against sysfs readers of the target list. A
fix for that is saved for a later patch.

Fixes: a5c258021689 ("cxl/bus: Populate the target list at decoder create")
Cc:  <stable@vger.kernel.org>
Signed-off-by: Huang, Ying <ying.huang@intel.com>
[djbw: rewrite the changelog, find the Fixes: tag]
Co-developed-by: Dan Williams <dan.j.williams@intel.com>
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>
---

diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index b7c93bb18f6e7..57495cdc181fd 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -1644,7 +1644,7 @@ static int decoder_populate_targets(struct cxl_switch_decoder *cxlsd,
 		return -EINVAL;
 
 	write_seqlock(&cxlsd->target_lock);
-	for (i = 0; i < cxlsd->nr_targets; i++) {
+	for (i = 0; i < cxlsd->cxld.interleave_ways; i++) {
 		struct cxl_dport *dport = find_dport(port, target_map[i]);
 
 		if (!dport) {