From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 03341CE7B1E for ; Fri, 14 Nov 2025 15:16:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=3wtNiwO7mQgs61ieJ83HPyGKadANIMB4TUgH9LUJTDI=; b=IQsbdIlHgaNbN5RQO3g5BIw97K gL4hGRHgsjEjYOhZPVoejROSAFQ5bOq7qOqtDApbYegbEKEb6ax7o3Ff446ZhAHyUsNlljoLF8h8G 6i5lyCiR+da9nlcrvRwd+sFBAF2K77+gT7CrzyICsj6EeHeJyGAf/+E0rnjVi9fzFTyth7mYAxBL/ UnyLBmUIaQ8MA+OwL7+pYxlhFgMm75EXBZ+r0ALPoW6limMbgQsdbKhkQ715o81yZoMqgo/os7VQM cfiZ4txxmNrMgVXO+mv3yYjWB1mwGqak4KU7XKLTbc9Xr9YfvowqnBoiGEabHbCnaSbrP7hppsVia Axm2V3Ug==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vJvXP-0000000CUjd-06Ma; Fri, 14 Nov 2025 15:16:35 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vJvXK-0000000CUh2-0clK for linux-arm-kernel@lists.infradead.org; Fri, 14 Nov 2025 15:16:31 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1763133389; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3wtNiwO7mQgs61ieJ83HPyGKadANIMB4TUgH9LUJTDI=; b=dUNv8OLQ5Q6GCAWsl7yLnwZud+8tsWk/3AjPJjsPfCICsadNpvO3BkQddMVkrkn70JI45Y ACDXwK4yknmdAG1L0PdgFFTfAp3TN+5rIZE9gr4YPkVydmKCJ25l0VsICpO591wjJBLmOf AKwu+TpNsLFDYJAIjQGbrD7YBFLw85M= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-530-KUYqLZu4MQq0ZGtzVQ5_Tw-1; Fri, 14 Nov 2025 10:16:26 -0500 X-MC-Unique: KUYqLZu4MQq0ZGtzVQ5_Tw-1 X-Mimecast-MFC-AGG-ID: KUYqLZu4MQq0ZGtzVQ5_Tw_1763133376 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 286521956094; Fri, 14 Nov 2025 15:16:16 +0000 (UTC) Received: from vschneid-thinkpadt14sgen2i.remote.csb (unknown [10.45.226.10]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id EF3DD1800451; Fri, 14 Nov 2025 15:15:59 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, rcu@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Frederic Weisbecker , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnaldo Carvalho de Melo , Josh Poimboeuf , Paolo Bonzini , Arnd Bergmann , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Sami Tolvanen , "David S. Miller" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Mel Gorman , Andrew Morton , Masahiro Yamada , Han Shen , Rik van Riel , Jann Horn , Dan Carpenter , Oleg Nesterov , Juri Lelli , Clark Williams , Yair Podemsky , Marcelo Tosatti , Daniel Wagner , Petr Tesarik , Shrikanth Hegde Subject: [PATCH v7 26/31] x86/jump_label: Add ASM support for static_branch_likely() Date: Fri, 14 Nov 2025 16:14:23 +0100 Message-ID: <20251114151428.1064524-6-vschneid@redhat.com> In-Reply-To: <20251114150133.1056710-1-vschneid@redhat.com> References: <20251114150133.1056710-1-vschneid@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251114_071630_256224_F37AFD04 X-CRM114-Status: GOOD ( 16.47 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org A later commit will add some early entry code that only needs to be executed if nohz_full is present on the cmdline, not just if CONFIG_NO_HZ_FULL is compiled in. Add an ASM-callable static branch macro. Note that I haven't found a way to express unlikely (i.e. out-of-line) static branches in ASM macros without using extra jumps, which kind of defeats the purpose. Consider: .macro FOOBAR // Key enabled: JMP .Ldostuff_\@ // Key disabled: NOP STATIC_BRANCH_UNLIKELY key, .Ldostuff_\@ // Patched to JMP if enabled jmp .Lend_\@ .Ldostuff_\@: .Lend_\@: .endm Instead, this should be expressed as a likely (i.e. in-line) static key: .macro FOOBAR // Key enabled: NOP // Key disabled: JMP .Lend_\@ STATIC_BRANCH_LIKELY key, .Lend\@ // Patched to NOP if enabled .Lend_\@: .endm Suggested-by: Frederic Weisbecker Signed-off-by: Valentin Schneider --- arch/x86/include/asm/jump_label.h | 33 ++++++++++++++++++++++++++++++- 1 file changed, 32 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h index 61dd1dee7812e..3c9ba3948e225 100644 --- a/arch/x86/include/asm/jump_label.h +++ b/arch/x86/include/asm/jump_label.h @@ -7,7 +7,38 @@ #include #include -#ifndef __ASSEMBLER__ +#ifdef __ASSEMBLER__ + +/* + * There isn't a neat way to craft unlikely static branches in ASM, so they + * all have to be expressed as likely (inline) static branches. This macro + * thus assumes a "likely" usage. + */ +.macro ARCH_STATIC_BRANCH_LIKELY_ASM key, label, jump, hack +1: +.if \jump || \hack + jmp \label +.else + .byte BYTES_NOP5 +.endif + .pushsection __jump_table, "aw" + _ASM_ALIGN + .long 1b - . + .long \label - . + /* LIKELY so bit0=1, bit1=hack */ + _ASM_PTR \key + 1 + (\hack << 1) - . + .popsection +.endm + +.macro STATIC_BRANCH_TRUE_LIKELY key, label + ARCH_STATIC_BRANCH_LIKELY_ASM \key, \label, 0, IS_ENABLED(CONFIG_HAVE_JUMP_LABEL_HACK) +.endm + +.macro STATIC_BRANCH_FALSE_LIKELY key, label + ARCH_STATIC_BRANCH_LIKELY_ASM \key, \label, 1, 0 +.endm + +#else /* !__ASSEMBLER__ */ #include #include -- 2.51.0