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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AF8C7C433F5 for ; Fri, 7 Oct 2022 19:26:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229791AbiJGTZ6 (ORCPT ); Fri, 7 Oct 2022 15:25:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59794 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230215AbiJGTY6 (ORCPT ); Fri, 7 Oct 2022 15:24:58 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B1FC7895E6 for ; Fri, 7 Oct 2022 12:24:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=PbGi9qswumamHM20nhxfQsLsToNlE1XdvdzMw825Asw=; b=n1HjNK6j+ySYzF0jmf7hO08NC6 OZUkag0tS3c3NjWrqvAJKTbVw1SCFuEtdDXbwtTrFQgK0BDvpJ0STHMrTVcr8tB5b3ovRBYS2EAmf 6ZEXdP+sATJnNdJ/iy3gRHgaG8KiRglDjRjXzasN8IUjqGHMKKDxpVPd94alBPAQwl0DsuhUZQ7V6 fZo2Tpsrh99lOipo4ImRJk/Y/p7RN+o1RPLuP6pLkSHVWwzeXCBsWUXA1xcVGNxKrh/fk62aaNFJc bH7RlPi8CGLhInNP4Uhd2mDDpWzQgiO9QaOF6loDfbege6tm5tqx4DMbzEbX3bNHj4aw7ec7prxdq mHV78J6Q==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1ogsxG-00284U-CC; Fri, 07 Oct 2022 19:24:19 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 7AD92300205; Fri, 7 Oct 2022 21:24:13 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 645C92C0F480E; Fri, 7 Oct 2022 21:24:13 +0200 (CEST) Date: Fri, 7 Oct 2022 21:24:13 +0200 From: Peter Zijlstra To: "Li, Xin3" Cc: "linux-kernel@vger.kernel.org" , "x86@kernel.org" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "hpa@zytor.com" Subject: Re: [PATCH 6/6] x86/gsseg: use the LKGS instruction if available for load_gs_index() Message-ID: References: <20221006154041.13001-1-xin3.li@intel.com> <20221006154041.13001-7-xin3.li@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 07, 2022 at 06:01:06PM +0000, Li, Xin3 wrote: > > > + alternative_io("1: call asm_load_gs_index\n" > > > + ".pushsection \".fixup\",\"ax\"\n" > > > + "2: xorl %k[sel], %k[sel]\n" > > > + " jmp 1b\n" > > > + ".popsection\n" > > > + _ASM_EXTABLE(1b, 2b), > > > + _ASM_BYTES(0x3e) LKGS_DI, > > > + X86_FEATURE_LKGS, > > > + ASM_OUTPUT2([sel] "+D" (sel), ASM_CALL_CONSTRAINT), > > > + ASM_NO_INPUT_CLOBBER(_ASM_AX)); > > > } > > > > I'm very sure none of this was tested... the .fixup section hasn't existed for > > almost a year now. > > Weird, did you ever check a kernel dump? $ readelf -WS defconfig-build/vmlinux | grep fixup [ 5] .pci_fixup PROGBITS ffffffff826a5350 18a5350 003570 00 A 0 0 16 [ 6] .rela.pci_fixup RELA 0000000000000000 360c388 005028 18 I 60 5 8 In fact, when I add one I get: ld: warning: orphan section `.fixup' from `arch/x86/kernel/traps.o' being placed in section `.fixup'