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=-2.3 required=3.0 tests=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 D9CD5C433FF for ; Mon, 29 Jul 2019 09:20:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC841206DD for ; Mon, 29 Jul 2019 09:20:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727830AbfG2JUR (ORCPT ); Mon, 29 Jul 2019 05:20:17 -0400 Received: from mail-wr1-f65.google.com ([209.85.221.65]:33626 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726496AbfG2JUQ (ORCPT ); Mon, 29 Jul 2019 05:20:16 -0400 Received: by mail-wr1-f65.google.com with SMTP id n9so61084134wru.0 for ; Mon, 29 Jul 2019 02:20:15 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:openpgp:message-id :date:user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=uXbHp4eBJvOivXe3gCAiTk5IMqXsOx6plzKSBZNiGpQ=; b=ZXg41ZBd57akSc5MyQ/G8Ib8s+ogudl6IpJM94ZHB0A0uwyMazRID0/42dJy9fIZN1 qBPdQzXccVo49/PBRDn5J5o7EOoA9VKTDu/S6YViHVXIdbIRE6qRY1OG4Gx2vA0ZtktD v2ehrtsrXNAqNQkAytDKD0Ghhfl9xVbtq+w7+EKaQOSgGm35KorZJa8F7epKNyf+oJLL 5yGTYwvJoeTtL3LgP4MObE9CrYtww11eo2fqmOQpVGZZnbUTt04MDu3O0UMqwl2C976E lwhiSW9jo96/INT+paXk58jnzldM+94+IO/WS678+vWs1/d2/oBimfdAzc2LOGXiGNUX Y66Q== X-Gm-Message-State: APjAAAV9ok5Oqy0sXDoCJ0zFuLhxcjdImoM0CLIoJUXntk9v7yZggaJi cWCHeUqWT7Nof1QvB7Gv2bguKbr0Va4= X-Google-Smtp-Source: APXvYqyLDdpNaY9V1WepUQO0fPV/p+GwAXZPJm4OXn15VZtBt43XB+wYaq6vIkAZVLbjYIdAAle3aw== X-Received: by 2002:adf:e6c5:: with SMTP id y5mr124260124wrm.235.1564392014705; Mon, 29 Jul 2019 02:20:14 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:29d3:6123:6d5f:2c04? ([2001:b07:6468:f312:29d3:6123:6d5f:2c04]) by smtp.gmail.com with ESMTPSA id w7sm69866212wrn.11.2019.07.29.02.20.13 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Mon, 29 Jul 2019 02:20:14 -0700 (PDT) Subject: Re: [PATCH v2 3/5] KVM: VMX: Add error handling to VMREAD helper To: Josh Poimboeuf , Sean Christopherson Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, Peter Zijlstra , "H. Peter Anvin" , kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20190719204110.18306-1-sean.j.christopherson@intel.com> <20190719204110.18306-4-sean.j.christopherson@intel.com> <20190728193641.mjxrtcc6ps72z3sp@treble> From: Paolo Bonzini Openpgp: preference=signencrypt Message-ID: Date: Mon, 29 Jul 2019 11:20:16 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190728193641.mjxrtcc6ps72z3sp@treble> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/07/19 21:36, Josh Poimboeuf wrote: > On Fri, Jul 19, 2019 at 01:41:08PM -0700, Sean Christopherson wrote: >> @@ -68,8 +67,22 @@ static __always_inline unsigned long __vmcs_readl(unsigned long field) >> { >> unsigned long value; >> >> - asm volatile (__ex_clear("vmread %1, %0", "%k0") >> - : "=r"(value) : "r"(field)); >> + asm volatile("1: vmread %2, %1\n\t" >> + ".byte 0x3e\n\t" /* branch taken hint */ >> + "ja 3f\n\t" >> + "mov %2, %%" _ASM_ARG1 "\n\t" >> + "xor %%" _ASM_ARG2 ", %%" _ASM_ARG2 "\n\t" >> + "2: call vmread_error\n\t" >> + "xor %k1, %k1\n\t" >> + "3:\n\t" >> + >> + ".pushsection .fixup, \"ax\"\n\t" >> + "4: mov %2, %%" _ASM_ARG1 "\n\t" >> + "mov $1, %%" _ASM_ARG2 "\n\t" >> + "jmp 2b\n\t" >> + ".popsection\n\t" >> + _ASM_EXTABLE(1b, 4b) >> + : ASM_CALL_CONSTRAINT, "=r"(value) : "r"(field) : "cc"); > > Was there a reason you didn't do the asm goto thing here like you did > for the previous patch? That seemed cleaner, and needs less asm. It's because asm goto doesn't support outputs. Paolo > I think the branch hints aren't needed -- they're ignored on modern > processors. Ditto for the previous patch. > > Also please use named asm operands whereever you can, like "%[field]" > instead of "%2". It helps a lot with readability. >