debug-token: Fix chunk header size issue
Correct NSM_DEBUG_TOKEN_INSTALL_CHUNK_SIZE to account for MCTP binding
header and NSM message header. Previous calculation missed protocol
headers, causing incorrect chunk size.
Tested:
1. Debug token install with payload greater than 4160 with GPU
2. Debug token install sanity all devices - with chunk and without
chunk
Fixes nvbug https://nvbugspro.nvidia.com/bug/5863102
Change-Id: I45c9cec899a758820de9b518fa64bfa80e9dfe99
Signed-off-by: Chinmay Shripad Hegde <chinmays@nvidia.com>
diff --git a/libnsm/debug-token.h b/libnsm/debug-token.h
index 2df9dca..0811fe5 100644
--- a/libnsm/debug-token.h
+++ b/libnsm/debug-token.h
@@ -29,18 +29,35 @@
#define NSM_DEBUG_TOKEN_ERASE_ALL_TOKENS 0xFFFFFFFF
#define NSM_DEBUG_TOKEN_ERASE_ALL_TOKENS_INCREMENT_RATCHET_COUNTER 0xFFFFFFFE
+/**
+ * @brief Size of MCTP binding header
+ *
+ * This includes:
+ * - 1 bit: IC (Integrity Check, always 0 for System Management API)
+ * - 7 bits: Message Type (0x7E for PCI Vendor Defined Message)
+ * Total: 1 byte
+ */
+#define MCTP_BINDING_HEADER_SIZE 1
+
/** @brief Calculate the optimal chunk size for token installation based on the
* maximum input buffer size. The chunk size is calculated by subtracting the
- * size of the fixed size variables present in the install token request header
- * from the maximum input buffer size.
+ * size of the fixed size variables and headers from the maximum input buffer
+ * size.
*
- * @param[in] buffer_size - Maximum input buffer size
- * @return Optimal chunk size
+ * Total overhead includes:
+ * - 1 byte: MCTP binding header (IC + Message Type = 0x7E)
+ * - 5 bytes: nsm_msg_hdr (PCI VID + Instance ID + OCP fields + NVIDIA msg type)
+ * - 6 bytes: nsm_common_req_v2 (command + reserved + data_size + reserved)
+ * - 12 bytes: chunk_offset + chunk_length + length_remaining
+ * Total: 24 bytes overhead
+ *
+ * @param[in] buffer_size - Maximum input buffer size (including all headers)
+ * @return Optimal chunk size (buffer_size - 24)
*/
#define NSM_DEBUG_TOKEN_INSTALL_CHUNK_SIZE(buffer_size) \
- (buffer_size - ((sizeof(struct nsm_install_token_req) - \
- sizeof(struct nsm_common_req_v2) - \
- sizeof(((struct nsm_install_token_req *)0)->data))))
+ (buffer_size - MCTP_BINDING_HEADER_SIZE - sizeof(struct nsm_msg_hdr) - \
+ (sizeof(struct nsm_install_token_req) - \
+ sizeof(((struct nsm_install_token_req *)0)->data)))
/** @brief NSM debug token type
*/
