From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit `objtool` errors such as: vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a: can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd The reason is that in such builds, the Clang invocation that compiles the combined Rust plus helpers bitcode emits LLVM bitcode (again) -- the final code generation happens in the linker's LTO step, which the `-mllvm` trap options passed to Clang do not reach. This, in turn, means that unreachable traps are missing, and the impossible paths do not merely fallthrough to the next symbol, but past the end of their own section, since LTO builds place each function in its own section. Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always emits machine code directly, with the traps in place. Assisted-by: LLM Cc: Gary Guo Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- Documentation/networking/smc-sysctl.rst | 140 ++++++++++++++++++++++++++++++++ 1 file changed, 140 insertions(+) create mode 100644 Documentation/networking/smc-sysctl.rst (limited to 'Documentation/networking/smc-sysctl.rst') diff --git a/Documentation/networking/smc-sysctl.rst b/Documentation/networking/smc-sysctl.rst new file mode 100644 index 000000000..93cc6244f --- /dev/null +++ b/Documentation/networking/smc-sysctl.rst @@ -0,0 +1,140 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========== +SMC Sysctl +========== + +/proc/sys/net/smc/* Variables +============================= + +autocorking_size - INTEGER + Setting SMC auto corking size: + SMC auto corking is like TCP auto corking from the application's + perspective of view. When applications do consecutive small + write()/sendmsg() system calls, we try to coalesce these small writes + as much as possible, to lower total amount of CDC and RDMA Write been + sent. + autocorking_size limits the maximum corked bytes that can be sent to + the under device in 1 single sending. If set to 0, the SMC auto corking + is disabled. + Applications can still use TCP_CORK for optimal behavior when they + know how/when to uncork their sockets. + + Default: 64K + +smcr_buf_type - INTEGER + Controls which type of sndbufs and RMBs to use in later newly created + SMC-R link group. Only for SMC-R. + + Default: 0 (physically contiguous sndbufs and RMBs) + + Possible values: + + - 0 - Use physically contiguous buffers + - 1 - Use virtually contiguous buffers + - 2 - Mixed use of the two types. Try physically contiguous buffers first. + If not available, use virtually contiguous buffers then. + +smcr_testlink_time - INTEGER + How frequently SMC-R link sends out TEST_LINK LLC messages to confirm + viability, after the last activity of connections on it. Value 0 means + disabling TEST_LINK. + + Default: 30 seconds. + +wmem - INTEGER + Initial size of send buffer used by SMC sockets. + + The minimum value is 16KiB and there is no hard limit for max value, but + only allowed 512KiB for SMC-R and 1MiB for SMC-D. + + Default: 64KiB + +rmem - INTEGER + Initial size of receive buffer (RMB) used by SMC sockets. + + The minimum value is 16KiB and there is no hard limit for max value, but + only allowed 512KiB for SMC-R and 1MiB for SMC-D. + + Default: 64KiB + +smcr_max_links_per_lgr - INTEGER + Controls the max number of links can be added to a SMC-R link group. Notice that + the actual number of the links added to a SMC-R link group depends on the number + of RDMA devices exist in the system. The acceptable value ranges from 1 to 2. Only + for SMC-R v2.1 and later. + + Default: 2 + +smcr_max_conns_per_lgr - INTEGER + Controls the max number of connections can be added to a SMC-R link group. The + acceptable value ranges from 16 to 255. Only for SMC-R v2.1 and later. + + Default: 255 + +smcr_max_send_wr - INTEGER + So-called work request buffers are SMCR link (and RDMA queue pair) level + resources necessary for performing RDMA operations. Since up to 255 + connections can share a link group and thus also a link and the number + of the work request buffers is decided when the link is allocated, + depending on the workload it can be a bottleneck in a sense that threads + have to wait for work request buffers to become available. Before the + introduction of this control the maximal number of work request buffers + available on the send path used to be hard coded to 16. With this control + it becomes configurable. The acceptable range is between 2 and 2048. + + Please be aware that all the buffers need to be allocated as a physically + continuous array in which each element is a single buffer and has the size + of SMC_WR_BUF_SIZE (48) bytes. If the allocation fails, we keep retrying + with half of the buffer count until it is either successful or (unlikely) + we dip below the old hard coded value which is 16 where we give up much + like before having this control. + + Default: 16 + +smcr_max_recv_wr - INTEGER + So-called work request buffers are SMCR link (and RDMA queue pair) level + resources necessary for performing RDMA operations. Since up to 255 + connections can share a link group and thus also a link and the number + of the work request buffers is decided when the link is allocated, + depending on the workload it can be a bottleneck in a sense that threads + have to wait for work request buffers to become available. Before the + introduction of this control the maximal number of work request buffers + available on the receive path used to be hard coded to 48. With this control + it becomes configurable. The acceptable range is between 2 and 2048. + + Please be aware that all the buffers need to be allocated as a physically + continuous array in which each element is a single buffer and has the size + of SMC_WR_BUF_SIZE (48) bytes. If the allocation fails, we keep retrying + with half of the buffer count until it is either successful or (unlikely) + we dip below the old hard coded value which is 48 where we give up much + like before having this control. + + Default: 48 + +limit_smc_hs - INTEGER + Whether to limit SMC handshake for newly created sockets. + + When enabled, SMC listen path applies handshake limitation based on + handshake worker congestion and queued SMC handshake load. + + Possible values: + + - 0 - Disable handshake limitation + - 1 - Enable handshake limitation + + Default: 0 (disable) + +hs_ctrl - STRING + Select the SMC handshake control profile by name. + + This string refers to the name of a user-implemented + BPF struct_ops instance of type smc_hs_ctrl. + + The selected profile controls whether SMC options are advertised + during TCP SYN/SYN-ACK handshake. + + Only available when CONFIG_SMC_HS_CTRL_BPF is enabled. + Write an empty string to clear the current profile. + + Default: empty string -- cgit v1.3.1