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McKenney" , Boqun Feng , Paolo Bonzini , Sean Christopherson , Wei Liu , Dexuan Cui , x86@kernel.org, Arnd Bergmann , Heiko Carstens , Christian Borntraeger , Sven Schnelle , Huacai Chen , Paul Walmsley , Palmer Dabbelt References: <20250908212737.353775467@linutronix.de> <20250908212926.033244852@linutronix.de> <45ce1b35-76ee-41b8-9fd2-b3b0d8126bf1@efficios.com> <87jz27vhs5.ffs@tglx> From: Mathieu Desnoyers Content-Language: en-US In-Reply-To: <87jz27vhs5.ffs@tglx> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: YQZPR01CA0124.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:c01:87::14) To YT2PR01MB9175.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:be::5) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: YT2PR01MB9175:EE_|YT2PR01MB9586:EE_ X-MS-Office365-Filtering-Correlation-Id: 3f921340-3252-4222-e3b8-08ddefb18806 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|7416014|376014; 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The function call overhead is larger than the >>> function itself. >> >> I'm wondering if there is a reason for making those actual functions and >> not inlines. >> >> The functions sit in kernel/entry/common.c, which are built with >> specific compiler flags in kernel/entry/Makefile: >> >> # Prevent the noinstr section from being pestered by sanitizer and other >> goodies >> # as long as these things cannot be disabled per function. >> KASAN_SANITIZE := n >> UBSAN_SANITIZE := n >> KCOV_INSTRUMENT := n >> >> # Branch profiling isn't noinstr-safe >> ccflags-$(CONFIG_TRACE_BRANCH_PROFILING) += -DDISABLE_BRANCH_PROFILING >> >> CFLAGS_REMOVE_common.o = -fstack-protector -fstack-protector-strong >> CFLAGS_common.o += -fno-stack-protector >> >> So I wonder if we're not breaking something in the area of "noinstr" >> tagging by inlining those into their caller ? > > No, because the call sites have to be non-instrumented as well. OK. Reviewed-by: Mathieu Desnoyers -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com