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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 8F4ECC76191 for ; Mon, 15 Jul 2019 12:37:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6DCD8206B8 for ; Mon, 15 Jul 2019 12:37:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730082AbfGOMhI (ORCPT ); Mon, 15 Jul 2019 08:37:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57102 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728933AbfGOMhH (ORCPT ); Mon, 15 Jul 2019 08:37:07 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5FEB9C057F2B; Mon, 15 Jul 2019 12:37:07 +0000 (UTC) Received: from treble (ovpn-120-170.rdu2.redhat.com [10.10.120.170]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2104960C4C; Mon, 15 Jul 2019 12:37:06 +0000 (UTC) Date: Mon, 15 Jul 2019 07:37:04 -0500 From: Josh Poimboeuf To: Paolo Bonzini Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Thomas Gleixner , Nick Desaulniers , Arnd Bergmann , Jann Horn , Randy Dunlap , Radim =?utf-8?B?S3LEjW3DocWZ?= Subject: Re: [PATCH 03/22] x86/kvm: Fix frame pointer usage in vmx_vmenter() Message-ID: <20190715123704.oke4pd4wguj5a7i3@treble> References: <299fe4adb78cff0a182f8376c23a445b94d7c782.1563150885.git.jpoimboe@redhat.com> <0b37031b-1043-8274-a086-2b5d0b02b5ef@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <0b37031b-1043-8274-a086-2b5d0b02b5ef@redhat.com> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Mon, 15 Jul 2019 12:37:07 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 15, 2019 at 11:04:03AM +0200, Paolo Bonzini wrote: > On 15/07/19 02:36, Josh Poimboeuf wrote: > > With CONFIG_FRAME_POINTER, vmx_vmenter() needs to do frame pointer setup > > before calling kvm_spurious_fault(). > > > > Fixes the following warning: > > > > arch/x86/kvm/vmx/vmenter.o: warning: objtool: vmx_vmenter()+0x14: call without frame pointer save/setup > > > > Signed-off-by: Josh Poimboeuf > > This is not enough, because the RSP value must match what is computed at > this place: > > /* Adjust RSP to account for the CALL to vmx_vmenter(). */ > lea -WORD_SIZE(%_ASM_SP), %_ASM_ARG2 > call vmx_update_host_rsp Ah, that is surprising :-) And then there's this, which overwrites the frame pointer anyway: mov VCPU_RBP(%_ASM_AX), %_ASM_BP Would it make sense to remove the call to vmx_vmenter() altogether, and just either embed it in __vmx_vcpu_run(), or jmp back and forth to it from __vmx_vcpu_run()? Then you could get rid of the RSP adjustment hack, and the vmx_update_host_rsp() function altogether. > Is this important since kvm_spurious_fault is just BUG()? It's probably only important if you care about the stack trace for the BUG() case. But BP is clobbered anyway so I guess it doesn't matter. > There is no macro currently to support CONFIG_DEBUG_BUGVERBOSE in > assembly code, but it's also fine if you just change the call to ud2. That would be one way to make objtool happy. -- Josh