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Sat, 07 Nov 2026 18:20:31 -0800 (PST) Received: from 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa ([118.217.70.161]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1b37314626dsm3027961c88.1.2026.11.07.18.20.28 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Sat, 07 Nov 2026 18:20:30 -0800 (PST) From: Jongwon Lee To: Davidlohr Bueso , Jonathan Cameron , Dave Jiang , Alison Schofield , Vishal Verma , Dan Williams Cc: Ira Weiny , Li Ming , Richard Cheng , linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v5 1/3] cxl/edac: Read cached DRAM event records under the xarray lock Date: Sun, 08 Nov 2026 11:20:23 +0900 Message-ID: <20261108022022.3352-2-ai@linux.com> In-Reply-To: <20261108022022.3352-1-ai@linux.com> References: <20261108022022.3352-1-ai@linux.com> Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 The event path caches DRAM event records in an xarray. It frees a record when xa_store() replaces it, when the record expires, and when the cache overflows. The event path runs with device_lock() and cxl_rwsem held for read. The repair path looks up records with cxl_find_rec_dram() while holding only cxl_rwsem for read, so both paths can run at the same time. cxl_find_rec_dram() reads the record after xa_load() returns, and cxl_mem_perform_sparing() reads validity_flags from the returned record again later. Both reads can hit a record that the event path has just freed. Move the lookup into __cxl_find_rec_dram(), which is called with the xarray lock held. cxl_find_rec_dram() now returns whether a record matched, and copies the matching record into a buffer passed in by the caller. The PPR path only needs to know whether there is a match, so it passes NULL. No caller keeps a pointer to the record after the lock is dropped. The event path frees a record only after xa_store() or xa_erase() has removed it from the xarray, and both of them take the same lock. Fixes: 0b5ccb0de1e2 ("cxl/edac: Support for finding memory operation attributes from the current boot") Fixes: 588ca944c277 ("cxl/edac: Add CXL memory device memory sparing control feature") Reported-by: Sashiko Closes: https://lore.kernel.org/r/sashiko-outbox-192042@kernel.org Reviewed-by: Richard Cheng Reviewed-by: Li Ming Signed-off-by: Jongwon Lee --- drivers/cxl/core/edac.c | 70 +++++++++++++++++++++++++++-------------- 1 file changed, 47 insertions(+), 23 deletions(-) diff --git a/drivers/cxl/core/edac.c b/drivers/cxl/core/edac.c index 34b81e8dfb..4624ab4644 100644 --- a/drivers/cxl/core/edac.c +++ b/drivers/cxl/core/edac.c @@ -938,18 +938,17 @@ cxl_find_rec_gen_media(struct cxl_memdev *cxlmd, return NULL; } +/* Caller holds the xarray lock. The record may be freed once it is dropped. */ static struct cxl_event_dram * -cxl_find_rec_dram(struct cxl_memdev *cxlmd, - struct cxl_mem_repair_attrbs *attrbs) +__cxl_find_rec_dram(struct xarray *rec_xarray, + struct cxl_mem_repair_attrbs *attrbs) { - struct cxl_mem_err_rec *array_rec = cxlmd->err_rec_array; struct cxl_event_dram *rec; u16 validity_flags; - if (!array_rec) - return NULL; + lockdep_assert_held(&rec_xarray->xa_lock); - rec = xa_load(&array_rec->rec_dram, attrbs->dpa); + rec = xa_load(rec_xarray, attrbs->dpa); if (!rec) return NULL; @@ -1029,6 +1028,30 @@ cxl_find_rec_dram(struct cxl_memdev *cxlmd, return NULL; } +/* + * cxl_store_rec_dram() replaces and frees records while the repair path only + * holds cxl_rwsem for read, so look the record up and read it under the + * xarray lock, and hand back a copy of the record. + */ +static bool cxl_find_rec_dram(struct cxl_memdev *cxlmd, + struct cxl_mem_repair_attrbs *attrbs, + struct cxl_event_dram *out) +{ + struct cxl_mem_err_rec *array_rec = cxlmd->err_rec_array; + struct cxl_event_dram *rec; + + if (!array_rec) + return false; + + xa_lock(&array_rec->rec_dram); + rec = __cxl_find_rec_dram(&array_rec->rec_dram, attrbs); + if (rec && out) + *out = *rec; + xa_unlock(&array_rec->rec_dram); + + return rec; +} + #define CXL_MAX_STORAGE_DAYS 10 #define CXL_MAX_STORAGE_TIME_SECS (CXL_MAX_STORAGE_DAYS * 24 * 60 * 60) @@ -1298,9 +1321,9 @@ cxl_mem_sparing_get_attrbs(struct cxl_mem_sparing_context *cxl_sparing_ctx) return 0; } -static struct cxl_event_dram * -cxl_mem_get_rec_dram(struct cxl_memdev *cxlmd, - struct cxl_mem_sparing_context *ctx) +static bool cxl_mem_get_rec_dram(struct cxl_memdev *cxlmd, + struct cxl_mem_sparing_context *ctx, + struct cxl_event_dram *rec) { struct cxl_mem_repair_attrbs attrbs = { 0 }; @@ -1332,10 +1355,10 @@ cxl_mem_get_rec_dram(struct cxl_memdev *cxlmd, attrbs.repair_type = CXL_RANK_SPARING; break; default: - return NULL; + return false; } - return cxl_find_rec_dram(cxlmd, &attrbs); + return cxl_find_rec_dram(cxlmd, &attrbs, rec); } static int @@ -1344,7 +1367,8 @@ cxl_mem_perform_sparing(struct device *dev, { struct cxl_memdev *cxlmd = cxl_sparing_ctx->cxlmd; struct cxl_memdev_sparing_in_payload sparing_pi; - struct cxl_event_dram *rec = NULL; + struct cxl_event_dram rec; + bool rec_found = false; u16 validity_flags = 0; int ret; @@ -1362,11 +1386,14 @@ cxl_mem_perform_sparing(struct device *dev, return -EBUSY; } else { if (cxl_is_memdev_memory_online(cxlmd)) { - rec = cxl_mem_get_rec_dram(cxlmd, cxl_sparing_ctx); - if (!rec) + rec_found = cxl_mem_get_rec_dram(cxlmd, cxl_sparing_ctx, + &rec); + if (!rec_found) return -EINVAL; - if (!get_unaligned_le16(rec->media_hdr.validity_flags)) + validity_flags = + get_unaligned_le16(rec.media_hdr.validity_flags); + if (!validity_flags) return -EINVAL; } } @@ -1376,13 +1403,10 @@ cxl_mem_perform_sparing(struct device *dev, if (cxl_sparing_ctx->persist_mode) sparing_pi.flags |= CXL_SET_HARD_SPARING(1); - if (rec) - validity_flags = get_unaligned_le16(rec->media_hdr.validity_flags); - switch (cxl_sparing_ctx->repair_type) { case EDAC_REPAIR_CACHELINE_SPARING: sparing_pi.column = cpu_to_le16(cxl_sparing_ctx->column); - if (!rec || (validity_flags & CXL_DER_VALID_SUB_CHANNEL)) { + if (!rec_found || (validity_flags & CXL_DER_VALID_SUB_CHANNEL)) { sparing_pi.flags |= CXL_SET_SPARING_SUB_CHNL_VALID(1); sparing_pi.sub_channel = cxl_sparing_ctx->sub_channel; } @@ -1399,9 +1423,9 @@ cxl_mem_perform_sparing(struct device *dev, fallthrough; default: sparing_pi.channel = cxl_sparing_ctx->channel; - if ((rec && (validity_flags & CXL_DER_VALID_NIBBLE)) || - (!rec && (!cxl_sparing_ctx->nibble_mask || - (cxl_sparing_ctx->nibble_mask & 0xFFFFFF)))) { + if ((rec_found && (validity_flags & CXL_DER_VALID_NIBBLE)) || + (!rec_found && (!cxl_sparing_ctx->nibble_mask || + (cxl_sparing_ctx->nibble_mask & 0xFFFFFF)))) { sparing_pi.flags |= CXL_SET_SPARING_NIB_MASK_VALID(1); put_unaligned_le24(cxl_sparing_ctx->nibble_mask, sparing_pi.nibble_mask); @@ -1814,7 +1838,7 @@ static int cxl_mem_perform_ppr(struct cxl_ppr_context *cxl_ppr_ctx) attrbs.repair_type = CXL_PPR; attrbs.dpa = cxl_ppr_ctx->dpa; attrbs.nibble_mask = cxl_ppr_ctx->nibble_mask; - if (!cxl_find_rec_dram(cxlmd, &attrbs) && + if (!cxl_find_rec_dram(cxlmd, &attrbs, NULL) && !cxl_find_rec_gen_media(cxlmd, &attrbs)) return -EINVAL; } -- 2.55.0