[PATCH v4 2/2] cxl/edac: Mask DPA flags in the event record cache key

[Jongwon Lee <ai@linux.com>]

The low bits of the DPA in a General Media or DRAM event record are
flags: bit 0 is VOLATILE and bit 1 is NOT_REPAIRABLE. The trace events
report the DPA with CXL_DPA_MASK applied, but cxl_store_rec_gen_media()
and cxl_store_rec_dram() use the raw value as the xarray key.

User space reads the DPA from the trace event and writes it to the
mem_repair dpa attribute. If the record had any flag set, xa_load()
misses it and the repair fails with -EINVAL. The raw key also lets a
repair go through for a record the device marked NOT_REPAIRABLE, if the
DPA is written with bit 1 set.

Key the records by the masked DPA and skip records marked
NOT_REPAIRABLE. cxl_find_rec_gen_media() now reads the record, so do
the lookup under the xarray lock as cxl_find_rec_dram() does, and
return a bool since its only caller tests the result.

Fixes: 0b5ccb0de1e2 ("cxl/edac: Support for finding memory operation attributes from the current boot")
Signed-off-by: Jongwon Lee <ai@linux.com>
---
 drivers/cxl/core/edac.c | 43 ++++++++++++++++++++++++++---------------
 1 file changed, 27 insertions(+), 16 deletions(-)

diff --git a/drivers/cxl/core/edac.c b/drivers/cxl/core/edac.c
index c5c8dda20e..a5f198b561 100644
--- a/drivers/cxl/core/edac.c
+++ b/drivers/cxl/core/edac.c
@@ -918,24 +918,37 @@ struct cxl_mem_repair_attrbs {
 	enum cxl_mem_repair_type repair_type;
 };
 
-static struct cxl_event_gen_media *
-cxl_find_rec_gen_media(struct cxl_memdev *cxlmd,
-		       struct cxl_mem_repair_attrbs *attrbs)
+/*
+ * The low bits of the event record DPA are flags (VOLATILE, NOT_REPAIRABLE).
+ * Records are looked up by the DPA user space writes back, which comes from
+ * the trace event and has the flags masked off, so key them the same way.
+ */
+static inline unsigned long cxl_rec_key(const struct cxl_event_media_hdr *hdr)
+{
+	return le64_to_cpu(hdr->phys_addr) & CXL_DPA_MASK;
+}
+
+static inline bool cxl_rec_not_repairable(const struct cxl_event_media_hdr *hdr)
+{
+	return le64_to_cpu(hdr->phys_addr) & CXL_DPA_NOT_REPAIRABLE;
+}
+
+static bool cxl_find_rec_gen_media(struct cxl_memdev *cxlmd,
+				   struct cxl_mem_repair_attrbs *attrbs)
 {
 	struct cxl_mem_err_rec *array_rec = cxlmd->err_rec_array;
 	struct cxl_event_gen_media *rec;
+	bool found;
 
-	if (!array_rec)
-		return NULL;
+	if (!array_rec || attrbs->repair_type != CXL_PPR)
+		return false;
 
+	xa_lock(&array_rec->rec_gen_media);
 	rec = xa_load(&array_rec->rec_gen_media, attrbs->dpa);
-	if (!rec)
-		return NULL;
+	found = rec && !cxl_rec_not_repairable(&rec->media_hdr);
+	xa_unlock(&array_rec->rec_gen_media);
 
-	if (attrbs->repair_type == CXL_PPR)
-		return rec;
-
-	return NULL;
+	return found;
 }
 
 /* Caller holds the xarray lock. The record may be freed once it is dropped. */
@@ -949,7 +962,7 @@ __cxl_find_rec_dram(struct xarray *rec_xarray,
 	lockdep_assert_held(&rec_xarray->xa_lock);
 
 	rec = xa_load(rec_xarray, attrbs->dpa);
-	if (!rec)
+	if (!rec || cxl_rec_not_repairable(&rec->media_hdr))
 		return NULL;
 
 	validity_flags = get_unaligned_le16(rec->media_hdr.validity_flags);
@@ -1130,8 +1143,7 @@ int cxl_store_rec_gen_media(struct cxl_memdev *cxlmd, union cxl_event *evt)
 		return -ENOMEM;
 
 	old_rec = xa_store(&array_rec->rec_gen_media,
-			   le64_to_cpu(rec->media_hdr.phys_addr), rec,
-			   GFP_KERNEL);
+			   cxl_rec_key(&rec->media_hdr), rec, GFP_KERNEL);
 	if (xa_is_err(old_rec)) {
 		kfree(rec);
 		return xa_err(old_rec);
@@ -1160,8 +1172,7 @@ int cxl_store_rec_dram(struct cxl_memdev *cxlmd, union cxl_event *evt)
 		return -ENOMEM;
 
 	old_rec = xa_store(&array_rec->rec_dram,
-			   le64_to_cpu(rec->media_hdr.phys_addr), rec,
-			   GFP_KERNEL);
+			   cxl_rec_key(&rec->media_hdr), rec, GFP_KERNEL);
 	if (xa_is_err(old_rec)) {
 		kfree(rec);
 		return xa_err(old_rec);
-- 
2.55.0