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Specifically, the CXL RAS UCE header log size is incorrectly defined in drivers/cxl/cxl.h. The UCE header log size is currently defined as 128 u32s (512 bytes), whereas it should be 16 u32s (64 bytes) per CXL r4.0 8.2.4.17.7. Correcting this will change the trace format and break the existing ABI contract with rasdaemon. How would you recommend proceeding to resolve this? I’ve included the Sashiko review comments here: commit 07869896095a6c3e7f10bf70e3c8c7b3f11530e1 Author: Terry Bowman cxl: Fix CXL_HEADERLOG_SIZE to match RAS Capability size This patch corrects CXL_HEADERLOG_SIZE from SZ_512 (512 bytes) to 64 bytes to match the actual size of the Header Log field in the CXL RAS Capability Structure. The old value caused header_log_copy() to overrun its iomap mapping, and caused the cxl_aer_uncorrectable_error trace event to memcpy 448 bytes of kernel stack into the ring buffer. > diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h > index 1297594beaec..3e69bcdbbbed 100644 > --- a/drivers/cxl/cxl.h > +++ b/drivers/cxl/cxl.h > @@ -158,8 +158,8 @@ static inline int ways_to_eiw(unsigned int ways, u8 *eiw) > #define CXL_RAS_CAP_CONTROL_FE_MASK GENMASK(5, 0) > #define CXL_RAS_HEADER_LOG_OFFSET 0x18 > #define CXL_RAS_CAPABILITY_LENGTH 0x58 > -#define CXL_HEADERLOG_SIZE SZ_512 > -#define CXL_HEADERLOG_SIZE_U32 SZ_512 / sizeof(u32) > +#define CXL_HEADERLOG_SIZE 64 > +#define CXL_HEADERLOG_SIZE_U32 (CXL_HEADERLOG_SIZE / sizeof(u32)) [ ... ] The commit message acknowledges that this shrinks the header_log array in both cxl_aer_uncorrectable_error and cxl_port_aer_uncorrectable_error from 128 u32s to 16 u32s, changing the binary trace event ABI. The event format exposed at: /sys/kernel/tracing/events/cxl/cxl_aer_uncorrectable_error/format will reflect the new smaller layout after this patch. Userspace tools such as rasdaemon, perf, and trace-cmd that were built against the old format file and hardcode 128 u32s (512 bytes) for header_log will silently misparse events from a patched kernel -- reading the 448 bytes of unrelated ring-buffer data that follow as though they were part of the header_log field, and computing wrong offsets for any field after it. The old 512-byte size was always wrong per the spec, so no correctly written tool could have fully relied on it. But does the Cc: stable tag risk propagating this ABI change to stable kernels where production CXL RAS monitoring tools may have been written against what was, however incorrectly, a previously stable layout? Is there a way to accompany this with a tools/ or Documentation/ update to help userspace consumers detect and adapt to the new format, rather than silently misparsing it? [1] - https://lore.kernel.org/linux-cxl/20260505173029.2718246-1-terry.bowman@amd.com/ Regards, Terry