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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_2 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 CCA25C2D0F6 for ; Wed, 13 May 2020 02:02:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA49420714 for ; Wed, 13 May 2020 02:02:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728384AbgEMCCe (ORCPT ); Tue, 12 May 2020 22:02:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:48152 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726287AbgEMCCe (ORCPT ); Tue, 12 May 2020 22:02:34 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A6FCA206CC; Wed, 13 May 2020 02:02:31 +0000 (UTC) Date: Tue, 12 May 2020 22:02:30 -0400 From: Steven Rostedt To: Thomas Gleixner Cc: LKML , x86@kernel.org, "Paul E. McKenney" , Andy Lutomirski , Alexandre Chartre , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Mathieu Desnoyers , Josh Poimboeuf , Will Deacon , Tom Lendacky , Wei Liu , Michael Kelley , Jason Chen CJ , Zhao Yakui , "Peter Zijlstra (Intel)" Subject: Re: [patch V5 02/38] x86/entry/64: Use native swapgs in asm_native_load_gs_index() Message-ID: <20200512220230.629a230f@oasis.local.home> In-Reply-To: <20200512213809.583980272@linutronix.de> References: <20200512210059.056244513@linutronix.de> <20200512213809.583980272@linutronix.de> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 12 May 2020 23:01:01 +0200 Thomas Gleixner wrote: > When PARAVIRT_XXL is in use, then load_gs_index() uses > xen_load_gs_index() and (asm_))native_load_gs_index() is unused. > > It's therefore pointless to use the paravirtualized SWAPGS implementation > in asm_native_load_gs_index(). Switch it to a plain swapgs. > > Signed-off-by: Thomas Gleixner > Cc: Juergen Gross > --- > arch/x86/entry/entry_64.S | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -1043,11 +1043,11 @@ idtentry simd_coprocessor_error do_simd > */ > SYM_FUNC_START(asm_native_load_gs_index) Small nit, but I would just call this: asm_load_gs_index. The "native" word is usually reserved for functions that are for bare metal and have a paravirt counterpart. As there is a native_load_gs_index(), I don't envision a need for a paravirt version of the asm function. Other than that. Reviewed-by: Steven Rostedt (VMware) -- Steve > FRAME_BEGIN > - SWAPGS > + swapgs > .Lgs_change: > movl %edi, %gs > 2: ALTERNATIVE "", "mfence", X86_BUG_SWAPGS_FENCE > - SWAPGS > + swapgs > FRAME_END > ret > SYM_FUNC_END(asm_native_load_gs_index) > @@ -1057,7 +1057,7 @@ EXPORT_SYMBOL(asm_native_load_gs_index) > .section .fixup, "ax" > /* running with kernelgs */ > SYM_CODE_START_LOCAL_NOALIGN(.Lbad_gs) > - SWAPGS /* switch back to user gs */ > + swapgs /* switch back to user gs */ > .macro ZAP_GS > /* This can't be a string because the preprocessor needs to see it. */ > movl $__USER_DS, %eax