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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3253DE9A754 for ; Tue, 24 Mar 2026 09:50:34 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9B7F36B009D; Tue, 24 Mar 2026 05:50:33 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 98F186B009F; Tue, 24 Mar 2026 05:50:33 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 87EFF6B00A0; Tue, 24 Mar 2026 05:50:33 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 75D606B009D for ; Tue, 24 Mar 2026 05:50:33 -0400 (EDT) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 3E4311A194D for ; Tue, 24 Mar 2026 09:50:33 +0000 (UTC) X-FDA: 84580486746.25.3BDEF8F Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf30.hostedemail.com (Postfix) with ESMTP id 439358000E for ; Tue, 24 Mar 2026 09:50:31 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=IBwqfW3D; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf30.hostedemail.com: domain of vschneid@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=vschneid@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1774345831; a=rsa-sha256; cv=none; b=05/PXH9vL79Shwq29UEUWropRFrXKUUZFCEsjsRBzu+7zwEgsRpJKpsMI/DVrlY7VqUuSg 0Tr7iNHLtK3Kri457hBaVP/EflJ0ay2nOda0aFLcPDEfUu/rHg0INoyfJQ/HEZroOMACMO 9qGTDUYi96mnsGRrVL89ELBThAKSqL0= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=IBwqfW3D; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf30.hostedemail.com: domain of vschneid@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=vschneid@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1774345831; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Gs9VmOHHSiH2vTwCJERGvoDC9R184iNrGHNb0XwJL0A=; b=FWoZvysM15RJE0s8yUmtGG8N8paNp+6e8a2jIYoNPgTGSSynSZsA4Bdig6OsNgz1oxPTZ/ 2dFpYPoQDqiwEkM4WJxigsfumDibeonh1ecVYPO/ChOEfiSW/H1wRSw2XjkW/rPYm84cRb mw5vS3+7C1mAFxP1amBePv56QLL8m7Y= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1774345830; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Gs9VmOHHSiH2vTwCJERGvoDC9R184iNrGHNb0XwJL0A=; b=IBwqfW3Ddc1KER8lPA0w9InMjdEEnobBfyTunjSlj1JvMtpdynmwyH0RqpRV69/ANQQ3qV nGK1MBmyx8fuJUyB6MUp8lpdG1ry/KhsIUDlB5hHZaZ0rvY+hxMBNAy+P7XK9zxbgxFpMa D+jXuB/AnhO44B7bUXqybr6s6cmBLzU= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-445-V_v494rdMsmtuLvusHWzzw-1; Tue, 24 Mar 2026 05:50:25 -0400 X-MC-Unique: V_v494rdMsmtuLvusHWzzw-1 X-Mimecast-MFC-AGG-ID: V_v494rdMsmtuLvusHWzzw_1774345821 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 72B261800281; Tue, 24 Mar 2026 09:50:21 +0000 (UTC) Received: from vschneid-thinkpadt14sgen2i.remote.csb (unknown [10.44.34.246]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0B28C300019F; Tue, 24 Mar 2026 09:50:08 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@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 , Tomas Glozar , Yair Podemsky , Marcelo Tosatti , Daniel Wagner , Petr Tesarik , Shrikanth Hegde Subject: [RFC PATCH v8 07/10] x86/jump_label: Add ASM support for static_branch_likely() Date: Tue, 24 Mar 2026 10:47:58 +0100 Message-ID: <20260324094801.3092968-8-vschneid@redhat.com> In-Reply-To: <20260324094801.3092968-1-vschneid@redhat.com> References: <20260324094801.3092968-1-vschneid@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-MFC-PROC-ID: cQP-gogDWQI_1ZsMLUO-R2rmD-Biygsqc3VCIYdmoWY_1774345821 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Rspamd-Queue-Id: 439358000E X-Stat-Signature: hanntentn7h7b1gowykr58d157k6zfh5 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1774345831-357708 X-HE-Meta: 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 ENZzoA+n 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 05b16299588d5..ea587598abe7c 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 -- 2.52.0