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=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 F25B3C2D0A3 for ; Tue, 3 Nov 2020 18:54:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9304320786 for ; Tue, 3 Nov 2020 18:54:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729542AbgKCSy2 (ORCPT ); Tue, 3 Nov 2020 13:54:28 -0500 Received: from gate.crashing.org ([63.228.1.57]:48218 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725957AbgKCSy2 (ORCPT ); Tue, 3 Nov 2020 13:54:28 -0500 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 0A3IlenB030027; Tue, 3 Nov 2020 12:47:40 -0600 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 0A3Ildp9030025; Tue, 3 Nov 2020 12:47:39 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Tue, 3 Nov 2020 12:47:39 -0600 From: Segher Boessenkool To: Borislav Petkov Cc: shuo.a.liu@intel.com, linux-kernel@vger.kernel.org, x86@kernel.org, Greg Kroah-Hartman , "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , Sean Christopherson , Yu Wang , Reinette Chatre , Yakui Zhao , Dave Hansen , Dan Williams , Fengwei Yin , Zhi Wang , Zhenyu Wang , Arvind Sankar , Peter Zijlstra , Nick Desaulniers Subject: Re: [PATCH v5 04/17] x86/acrn: Introduce hypercall interfaces Message-ID: <20201103184739.GL2672@gate.crashing.org> References: <20201019061803.13298-5-shuo.a.liu@intel.com> <20201102145657.GD15392@zn.tnic> <20201102160901.GU2672@gate.crashing.org> <20201102171950.GF15392@zn.tnic> <20201102181000.GX2672@gate.crashing.org> <20201102183430.GG15392@zn.tnic> <20201102200113.GY2672@gate.crashing.org> <20201102225439.GI15392@zn.tnic> <20201102231809.GC2672@gate.crashing.org> <20201103164435.GB4111@zn.tnic> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201103164435.GB4111@zn.tnic> User-Agent: Mutt/1.4.2.3i Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 03, 2020 at 05:44:35PM +0100, Borislav Petkov wrote: > On Mon, Nov 02, 2020 at 05:18:09PM -0600, Segher Boessenkool wrote: > > That is invalid actually: local register asm as input to an inline asm > > should use *that* register! > > > > This is all correct until LRA ("reload"). Not that "movl %xmm0,$eax" > > works, but at least it screams its head off, as it should. > > Screams how? $ cat xmm1.s movl %xmm0,%eax $ x86_64-linux-as xmm1.s -o xmm1.o xmm1.s: Assembler messages: xmm1.s:1: Error: unsupported instruction `mov' (This isn't an existing insn IIUC.) > It builds fine without a single peep with -Wall here. > > Btw, that's a MOVD - not a MOVL. MOVD can do xmm -> gpr moves. And > singlestepping it with gdb does, well, something, which is clearly > wrong but nothing complains: > > => 0x555555555131 : movd %xmm0,%eax > > and %xmm0 has: > > (gdb) p $xmm0 > $2 = {v4_float = {0.99000001, 0, 0, 0}, v2_double = {5.2627153433055495e-315, 0}, v16_int8 = {-92, 112, 125, 63, > ^^^^^^^^^^ > > so that is correct. The original code had movl. And movl is needed for GPRs. > and that same value goes into %r8d: > > mov %eax,%r8d Which violates what is required by register asm :-( > > Yes. But GCC doing what you should have said instead of doing what you > > said, is not good. > > Oh well, should I open a low prio bug, would that help? Sure, thanks! > I probably should test with the latest gcc first, though... Yeah... FWIW, I tested with x86_64-linux-gcc (GCC) 11.0.0 20201015 (experimental) so I doubt current ToT will have it fixed, but who knows. Thanks, Segher