On Tue, Sep 03, 2024 at 08:41:44PM +0800, Zijun Hu wrote:

From: Zijun Hu quic_zijuhu@quicinc.com

match_free_decoder()'s logic for finding a free cxl decoder depends on a prerequisite that all child decoders are sorted by ID in ascending order but the prerequisite may not be guaranteed, fix by finding a free cxl decoder with minimal ID.

After reading the 'Closes' tag below I have a better understanding of why you may be doing this, but I don't want to have to jump to that Link. Can you describe here examples of when the ordered allocation may not be guaranteed, and the impact when that happens.

This includes a change to device_for_each_child() which I see mentioned in the Closes tag discussion too. Is that required for this fix?

It's feeling like the fix and api update are comingled. Please clarify.

Thanks, Alison

Fixes: 384e624bb211 ("cxl/region: Attach endpoint decoders") Closes: https://lore.kernel.org/all/cdfc6f98-1aa0-4cb5-bd7d-93256552c39b@icloud.com/ Cc: stable@vger.kernel.org Signed-off-by: Zijun Hu quic_zijuhu@quicinc.com

---

drivers/cxl/core/region.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c index 21ad5f242875..b9607b4fc40b 100644 --- a/drivers/cxl/core/region.c +++ b/drivers/cxl/core/region.c @@ -797,21 +797,26 @@ static size_t show_targetN(struct cxl_region *cxlr, char *buf, int pos) static int match_free_decoder(struct device *dev, void *data) { struct cxl_decoder *cxld;

• int *id = data;

• struct cxl_decoder *target_cxld;
• struct device **target_device = data;

if (!is_switch_decoder(dev)) return 0; cxld = to_cxl_decoder(dev);

• /* enforce ordered allocation */
• if (cxld->id != *id)

• if (cxld->region) return 0;

• if (!cxld->region)

• return 1;
  

• (*id)++;

• if (!*target_device) {

• *target_device = get_device(dev);
  

• return 0;
  

• }
• /* enforce ordered allocation */
• target_cxld = to_cxl_decoder(*target_device);
• if (cxld->id < target_cxld->id) {

• put_device(*target_device);
  

• *target_device = get_device(dev);
  

• }

return 0; } @@ -839,8 +844,7 @@ cxl_region_find_decoder(struct cxl_port *port, struct cxl_endpoint_decoder *cxled, struct cxl_region *cxlr) {

• struct device *dev;
• int id = 0;

• struct device *dev = NULL;

if (port == cxled_to_port(cxled)) return &cxled->cxld; @@ -849,7 +853,8 @@ cxl_region_find_decoder(struct cxl_port *port, dev = device_find_child(&port->dev, &cxlr->params, match_auto_decoder); else

• dev = device_find_child(&port->dev, &id, match_free_decoder);
  

• /* Need to put_device(@dev) after use */
  

• device_for_each_child(&port->dev, &dev, match_free_decoder);
  

  if (!dev) return NULL; /*

---

base-commit: 67784a74e258a467225f0e68335df77acd67b7ab change-id: 20240903-fix_cxld-4f6575a90619

Best regards,

Zijun Hu quic_zijuhu@quicinc.com