From 27600805e62f800bacf990354632eae4e487d34c Mon Sep 17 00:00:00 2001 From: Yazen Ghannam Date: Thu, 3 Sep 2026 10:43:25 -0500 Subject: x86/amd_node: Fix PCI device reference counting in amd_smn_init() The local "root" pointer is a temporary variable used during the device search. Therefore, refcount related to the search iterators should be cleaned up after the search is complete. Use the __free() cleanup macro to ensure the refcount is decremented when the temporary pointer goes out of scope. Additionally, increment the refcount when caching a root pointer. This ensures the in-use refcount is separate from the temporary search refcounting. Finally, drop the redundant "root = NULL" before the second search loop. The pci_get_class() iterator always decrements the refcount of its "from" argument, so the first loop can only fall through with "root" already NULL. Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching") Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com Reported-by: Sashiko Assisted-by: LLM Signed-off-by: Yazen Ghannam Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Mario Limonciello (AMD) Cc: Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com --- Documentation/networking/netif-msg.rst | 95 ++++++++++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) create mode 100644 Documentation/networking/netif-msg.rst (limited to 'Documentation/networking/netif-msg.rst') diff --git a/Documentation/networking/netif-msg.rst b/Documentation/networking/netif-msg.rst new file mode 100644 index 000000000..b20d265a7 --- /dev/null +++ b/Documentation/networking/netif-msg.rst @@ -0,0 +1,95 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============== +NETIF Msg Level +=============== + +The design of the network interface message level setting. + +History +------- + + The design of the debugging message interface was guided and + constrained by backwards compatibility previous practice. It is useful + to understand the history and evolution in order to understand current + practice and relate it to older driver source code. + + From the beginning of Linux, each network device driver has had a local + integer variable that controls the debug message level. The message + level ranged from 0 to 7, and monotonically increased in verbosity. + + The message level was not precisely defined past level 3, but were + always implemented within +-1 of the specified level. Drivers tended + to shed the more verbose level messages as they matured. + + - 0 Minimal messages, only essential information on fatal errors. + - 1 Standard messages, initialization status. No run-time messages + - 2 Special media selection messages, generally timer-driver. + - 3 Interface starts and stops, including normal status messages + - 4 Tx and Rx frame error messages, and abnormal driver operation + - 5 Tx packet queue information, interrupt events. + - 6 Status on each completed Tx packet and received Rx packets + - 7 Initial contents of Tx and Rx packets + + Initially this message level variable was uniquely named in each driver + e.g. "lance_debug", so that a kernel symbolic debugger could locate and + modify the setting. When kernel modules became common, the variables + were consistently renamed to "debug" and allowed to be set as a module + parameter. + + This approach worked well. However there is always a demand for + additional features. Over the years the following emerged as + reasonable and easily implemented enhancements + + - Using an ioctl() call to modify the level. + - Per-interface rather than per-driver message level setting. + - More selective control over the type of messages emitted. + + The netif_msg recommendation adds these features with only a minor + complexity and code size increase. + + The recommendation is the following points + + - Retaining the per-driver integer variable "debug" as a module + parameter with a default level of '1'. + + - Adding a per-interface private variable named "msg_enable". The + variable is a bit map rather than a level, and is initialized as:: + + 1 << debug + + Or more precisely:: + + debug < 0 ? 0 : 1 << min(sizeof(int)-1, debug) + + Messages should changes from:: + + if (debug > 1) + printk(MSG_DEBUG "%s: ... + + to:: + + if (np->msg_enable & NETIF_MSG_LINK) + printk(MSG_DEBUG "%s: ... + + +The set of message levels is named + + + ========= =================== ============ + Old level Name Bit position + ========= =================== ============ + 0 NETIF_MSG_DRV 0x0001 + 1 NETIF_MSG_PROBE 0x0002 + 2 NETIF_MSG_LINK 0x0004 + 2 NETIF_MSG_TIMER 0x0004 + 3 NETIF_MSG_IFDOWN 0x0008 + 3 NETIF_MSG_IFUP 0x0008 + 4 NETIF_MSG_RX_ERR 0x0010 + 4 NETIF_MSG_TX_ERR 0x0010 + 5 NETIF_MSG_TX_QUEUED 0x0020 + 5 NETIF_MSG_INTR 0x0020 + 6 NETIF_MSG_TX_DONE 0x0040 + 6 NETIF_MSG_RX_STATUS 0x0040 + 7 NETIF_MSG_PKTDATA 0x0080 + ========= =================== ============ -- cgit v1.3.1