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 E2DA8C433FE for ; Fri, 18 Nov 2022 17:44:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235386AbiKRRom (ORCPT ); Fri, 18 Nov 2022 12:44:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40796 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234711AbiKRRok (ORCPT ); Fri, 18 Nov 2022 12:44:40 -0500 Received: from mail-pf1-x435.google.com (mail-pf1-x435.google.com [IPv6:2607:f8b0:4864:20::435]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D83DA30F59 for ; Fri, 18 Nov 2022 09:44:39 -0800 (PST) Received: by mail-pf1-x435.google.com with SMTP id b29so5514935pfp.13 for ; Fri, 18 Nov 2022 09:44:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=nArehU+M3JvjBQMdLR3MkhWwl9kcg6nFoz5gcIdq8kE=; b=AJca8AstvwdRRkP1srRFlRaPBpzypHw8skgW7f8bNMatvp8svOlFc5rCnpPMyeFAu+ 1/rvqCTFynexUfBUicBJcJOC6H1CZDeuWNiPY8kzV1WSlZFBRjcMErop2+JrLAtvg1DF aKG5zdmUfzjjLZbj0g18wlANBPod7aT5N/RF6f4FW98GrUzU7icRn5Sz/7yzmJ2raR27 yrJsXHI+rDfM1Ry2minZqoQs85Is74E+PADC3+rx+tkkrtXIXjalfKx+fvKTsEdWtgbq 4oV3qRJonSGXNPO+QrVxhnInnqt0BmuMec0nhqlL4F5qwORlQ9L/CaPiz/pU5tfk8xu9 xdYg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=nArehU+M3JvjBQMdLR3MkhWwl9kcg6nFoz5gcIdq8kE=; b=RorwNkGkuAKlUc0H6FzunXPR6MhPeIYrI5gnOciPAA7bZtJ+YaPHkeyJmbuuwmGy8E g7fAuR+xWQKM1/ZP7kMBDs8lLErUBT4tcyurl/3uLKkR/9SGgj6FGxVimM61ZFp2GK0H X8amYuSk1wvZZUamgLSZKrMQ5FiM0+kNn7zsXwXMagLLQhNEcAjeUpJPYKXE4855Bw9g X/VvntMjDXw1+h1qZd26IUVqZhKRH03fn9jBsVoHN5uuGGuWZ2jwtAmsbg2Lrypjc/R/ lHk+B5hiRN0p6mYR12fS7c2+RyXCXTI7WYeTP2A2e9NRMpd2g48JKIH+5crAw6l53Aj7 Y02g== X-Gm-Message-State: ANoB5pkuiGt1wfH6tWpSrdjgs+OCY8gHG3dveclpQYLQr146lL/jYlGq hdFM02Sj1PlgNn7DC6czhV8zvg== X-Google-Smtp-Source: AA0mqf7gyEVm/lIvuTjTM0XanOw0gnpUP2EsrJLFSLzMo9IOee6S/iHkyQ0EtRQ8Unb8HSLYW0d9kQ== X-Received: by 2002:a63:4d0d:0:b0:477:14ea:cee6 with SMTP id a13-20020a634d0d000000b0047714eacee6mr6045535pgb.303.1668793479252; Fri, 18 Nov 2022 09:44:39 -0800 (PST) Received: from google.com (7.104.168.34.bc.googleusercontent.com. [34.168.104.7]) by smtp.gmail.com with ESMTPSA id g8-20020aa79f08000000b0056bc5ad4862sm3456021pfr.28.2022.11.18.09.44.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Nov 2022 09:44:38 -0800 (PST) Date: Fri, 18 Nov 2022 17:44:35 +0000 From: Sean Christopherson To: Alexey Dobriyan Cc: pbonzini@redhat.com, kvm@vger.kernel.org Subject: Re: [PATCH] kvm, vmx: don't use "unsigned long" in vmx_vcpu_enter_exit() Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Nit (because I really suck at case-insensitive searches), please capitalize "KVM: VMX:" in the shortlog. On Fri, Nov 18, 2022, Alexey Dobriyan wrote: > __vmx_vcpu_run_flags() returns "unsigned int" and uses only 2 bits of it > so using "unsigned long" is very much pointless. And __vmx_vcpu_run() and vmx_spec_ctrl_restore_host() take an "unsigned int" as well, i.e. actually relying on an "unsigned long" value won't actually work. On a related topic, this code in __vmx_vcpu_run() is unnecessarily fragile as it relies on VMX_RUN_VMRESUME being in bits 0-7. /* Copy @flags to BL, _ASM_ARG3 is volatile. */ mov %_ASM_ARG3, %bl ... /* Check if vmlaunch or vmresume is needed */ testb $VMX_RUN_VMRESUME, %bl The "byte" logic is another holdover, from when "flags" was just "launched" and was passed in as a boolean. I'll send a proper patch to do: diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S index 0b5db4de4d09..5bd39f63497d 100644 --- a/arch/x86/kvm/vmx/vmenter.S +++ b/arch/x86/kvm/vmx/vmenter.S @@ -69,8 +69,8 @@ SYM_FUNC_START(__vmx_vcpu_run) */ push %_ASM_ARG2 - /* Copy @flags to BL, _ASM_ARG3 is volatile. */ - mov %_ASM_ARG3B, %bl + /* Copy @flags to EBX, _ASM_ARG3 is volatile. */ + mov %_ASM_ARG3L, %ebx lea (%_ASM_SP), %_ASM_ARG2 call vmx_update_host_rsp @@ -106,7 +106,7 @@ SYM_FUNC_START(__vmx_vcpu_run) mov (%_ASM_SP), %_ASM_AX /* Check if vmlaunch or vmresume is needed */ - testb $VMX_RUN_VMRESUME, %bl + test $VMX_RUN_VMRESUME, %ebx /* Load guest registers. Don't clobber flags. */ mov VCPU_RCX(%_ASM_AX), %_ASM_CX @@ -128,7 +128,7 @@ SYM_FUNC_START(__vmx_vcpu_run) /* Load guest RAX. This kills the @regs pointer! */ mov VCPU_RAX(%_ASM_AX), %_ASM_AX - /* Check EFLAGS.ZF from 'testb' above */ + /* Check EFLAGS.ZF from 'test VMX_RUN_VMRESUME' above */ jz .Lvmlaunch /* > Signed-off-by: Alexey Dobriyan > --- Reviewed-by: Sean Christopherson