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 X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8401CC43218 for ; Mon, 10 Jun 2019 18:34:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5EAA920862 for ; Mon, 10 Jun 2019 18:34:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387710AbfFJSea (ORCPT ); Mon, 10 Jun 2019 14:34:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46192 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726214AbfFJSea (ORCPT ); Mon, 10 Jun 2019 14:34:30 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 66615C18B2E5; Mon, 10 Jun 2019 18:34:29 +0000 (UTC) Received: from treble (ovpn-121-189.rdu2.redhat.com [10.10.121.189]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 67EC419C59; Mon, 10 Jun 2019 18:34:07 +0000 (UTC) Date: Mon, 10 Jun 2019 13:33:57 -0500 From: Josh Poimboeuf To: Peter Zijlstra Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Ard Biesheuvel , Andy Lutomirski , Steven Rostedt , Ingo Molnar , Thomas Gleixner , Linus Torvalds , Masami Hiramatsu , Jason Baron , Jiri Kosina , David Laight , Borislav Petkov , Julia Cartwright , Jessica Yu , "H. Peter Anvin" , Nadav Amit , Rasmus Villemoes , Edward Cree , Daniel Bristot de Oliveira Subject: Re: [PATCH 13/15] x86/static_call: Add inline static call implementation for x86-64 Message-ID: <20190610183357.zj6rwdpgw36anpfc@treble> References: <20190605130753.327195108@infradead.org> <20190605131945.313688119@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190605131945.313688119@infradead.org> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 10 Jun 2019 18:34:29 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 05, 2019 at 03:08:06PM +0200, Peter Zijlstra wrote: > --- a/arch/x86/include/asm/static_call.h > +++ b/arch/x86/include/asm/static_call.h > @@ -2,6 +2,20 @@ > #ifndef _ASM_STATIC_CALL_H > #define _ASM_STATIC_CALL_H > > +#include > + > +#ifdef CONFIG_HAVE_STATIC_CALL_INLINE > + > +/* > + * This trampoline is only used during boot / module init, so it's safe to use > + * the indirect branch without a retpoline. > + */ > +#define __ARCH_STATIC_CALL_TRAMP_JMP(key, func) \ > + ANNOTATE_RETPOLINE_SAFE \ > + "jmpq *" __stringify(key) "+" __stringify(SC_KEY_func) "(%rip) \n" > + > +#else /* !CONFIG_HAVE_STATIC_CALL_INLINE */ I wonder if we can simplify this (and drop the indirect branch) by getting rid of the above cruft, and instead just use the out-of-line trampoline as the default for inline as well. Then the inline case could fall back to the out-of-line implementation (by patching the trampoline's jmp dest) before static_call_initialized is set. -- Josh