[PATCH] cxl/events: Fix event type check for CME counter expiration

[Guixin Liu <kanie@linux.alibaba.com>]

The Memory Event Type field of the General Media and DRAM event
records is an enumeration; 05h designates the advanced programmable
CME counter expiration event. The validity checks for that event
test the field with a bitwise AND against
CXL_GMER_MEM_EVT_TYPE_AP_CME_COUNTER_EXPIRE instead of comparing it
for equality, so benign event types that share a bit with 05h, such
as 01h (Invalid Address), 03h (TE State Violation), 04h (Scrub
Media ECC Error) or 06h (CKID Violation), match too.

A device reporting any of those types with an otherwise valid record
therefore trips WARN_ON_ONCE, once the general media or DRAM
tracepoint is enabled, which is the case for any deployment
collecting CXL events with rasdaemon. The warning panics the kernel
under panic_on_warn=1.

Compare the type field for equality instead.

Found by code inspection during review of a downstream backport of
these two patches. Reproduced in a QEMU CXL topology by injecting a
General Media event with type 01h through the
cxl-inject-general-media-event QMP command, which warns in
cxl_event_trace_record(); with the fix the same injection is traced
without a warning. Events that do violate the spec conditions, type
05h without the threshold event descriptor bit and type 05h with the
bit set but a zero CME count, still warn.

Fixes: cd3b36cfc659 ("cxl/events: Add extra validity checks for corrected memory error count in General Media Event Record")
Fixes: d8145bb8af5c ("cxl/events: Add extra validity checks for CVME count in DRAM Event Record")
Cc: stable@vger.kernel.org
Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
---
 drivers/cxl/core/mbox.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index 55828a836c01..01341f524a93 100644
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -942,11 +942,11 @@ void cxl_event_trace_record(struct cxl_memdev *cxlmd,
 
 			if (evt->gen_media.media_hdr.descriptor &
 			    CXL_GMER_EVT_DESC_THRESHOLD_EVENT)
-				WARN_ON_ONCE((evt->gen_media.media_hdr.type &
+				WARN_ON_ONCE((evt->gen_media.media_hdr.type ==
 					      CXL_GMER_MEM_EVT_TYPE_AP_CME_COUNTER_EXPIRE) &&
 					     !get_unaligned_le24(evt->gen_media.cme_count));
 			else
-				WARN_ON_ONCE(evt->gen_media.media_hdr.type &
+				WARN_ON_ONCE(evt->gen_media.media_hdr.type ==
 					     CXL_GMER_MEM_EVT_TYPE_AP_CME_COUNTER_EXPIRE);
 
 			trace_cxl_general_media(cxlmd, type, cxlr, hpa,
@@ -957,11 +957,11 @@ void cxl_event_trace_record(struct cxl_memdev *cxlmd,
 
 			if (evt->dram.media_hdr.descriptor &
 			    CXL_GMER_EVT_DESC_THRESHOLD_EVENT)
-				WARN_ON_ONCE((evt->dram.media_hdr.type &
+				WARN_ON_ONCE((evt->dram.media_hdr.type ==
 					      CXL_DER_MEM_EVT_TYPE_AP_CME_COUNTER_EXPIRE) &&
 					     !get_unaligned_le24(evt->dram.cvme_count));
 			else
-				WARN_ON_ONCE(evt->dram.media_hdr.type &
+				WARN_ON_ONCE(evt->dram.media_hdr.type ==
 					     CXL_DER_MEM_EVT_TYPE_AP_CME_COUNTER_EXPIRE);
 
 			trace_cxl_dram(cxlmd, type, cxlr, hpa, hpa_alias,
-- 
2.43.7