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 B89D4C433F5 for ; Thu, 26 May 2022 23:14:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344338AbiEZXOl (ORCPT ); Thu, 26 May 2022 19:14:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41984 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231613AbiEZXOj (ORCPT ); Thu, 26 May 2022 19:14:39 -0400 Received: from mail.eskimo.com (mail.eskimo.com [204.122.16.222]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5DFD4E52A1; Thu, 26 May 2022 16:14:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=eskimo.com; s=default; t=1653606876; bh=brQFxuJo8vPS3y4lzGJlq1ypgd6jd/P+HXBTPOoOyyU=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=S58o+5zOf7LZhkXnDjwS3R/yU0J3HXSBryXqEyBtrNuHxqqji3Mzz9UCqw1fLjML1 /67CAA03CzJZMEh2uxdPWfcYO8KZ4xYnON9OEnIgiP77TJN9STKT1iyv8YlMTORKSb UjoHb1kYa2VJMTHEYZ5ezJbAc1097LIOaaH9uAfRLJclFEvlYkXLEagsU9jz4/VjHi TzWwArh8Wcnit5UVAboP8EESUPTdmWq04JehrpAkv0nuwRexy9PDE5u105L4YwF3ND By/i4yTqY19sggdhE6ZWu5pwwRhdGEi5z5ZolkbXzZFy5MnLLthaDxj+Hlsuwfe1qO 0oXSXH1r3cRQQ== Received: from ubuntu.eskimo.com (ubuntu.eskimo.com [204.122.16.33]) by mail.eskimo.com (Postfix) with ESMTPS id C93943CA09F; Thu, 26 May 2022 16:14:36 -0700 (PDT) Date: Thu, 26 May 2022 16:14:36 -0700 (PDT) From: Robert Dinse To: Sean Christopherson cc: Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Kees Cook Subject: Re: [PATCH v2 0/8] KVM: x86: Emulator _regs fixes and cleanups In-Reply-To: <20220526210817.3428868-1-seanjc@google.com> Message-ID: References: <20220526210817.3428868-1-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed X-Virus-Scanned: clamav-milter 0.103.6 at mail.eskimo.com X-Virus-Status: Clean Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It >DID< build ok with this patch, I applied it and built last night, I'm presently running that kernel with a KVM/Qemu Windows guest on my workstation: Linux nanook 5.18.0 #1 SMP PREEMPT Wed May 25 18:14:43 PDT 2022 x86_64 x86_64 x86_64 GNU/Linux The Windows guest starts and runs but networking isn't working (I am using a bridge for the guest hosts and a static IP for both the main machine and guest), it all works including networking with 5.17.9. -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_- Eskimo North Linux Friendly Internet Access, Shell Accounts, and Hosting. Knowledgeable human assistance, not telephone trees or script readers. See our web site: http://www.eskimo.com/ (206) 812-0051 or (800) 246-6874. On Thu, 26 May 2022, Sean Christopherson wrote: > Date: Thu, 26 May 2022 21:08:09 +0000 > From: Sean Christopherson > To: Paolo Bonzini > Cc: Sean Christopherson , > Vitaly Kuznetsov , > Wanpeng Li , Jim Mattson , > Joerg Roedel , kvm@vger.kernel.org, > linux-kernel@vger.kernel.org, Kees Cook , > Robert Dinse > Subject: [PATCH v2 0/8] KVM: x86: Emulator _regs fixes and cleanups > > Clean up and harden the use of the x86_emulate_ctxt._regs, which is > surrounded by a fair bit of magic. This series was prompted by bug reports > by Kees and Robert where GCC-12 flags an out-of-bounds _regs access. The > warning is a false positive due to a now-known GCC bug, but it's cheap and > easy to harden the _regs usage, and doing so minimizing the risk of more > precisely handling 32-bit vs. 64-bit GPRs. > > I didn't tag patch 2 with Fixes or Cc: stable@. It does remedy the > GCC-12 warning, but AIUI the GCC-12 bug affects other KVM paths that > already have explicit guardrails, i.e. fixing this one case doesn't > guarantee happiness when building with CONFIG_KVM_WERROR=y, let alone > CONFIG_WERROR=y. That said, it might be worth sending to the v5.18 stable > tree[*] as it does appear to make some configs/setups happy. > > [*] KVM hasn't changed, but the warning=>error was introduced in v5.18 by > commit e6148767825c ("Makefile: Enable -Warray-bounds"). > > v2: > - Collect reviews and tests. [Vitaly, Kees, Robert] > - Tweak patch 1's changelog to explicitly call out that dirty_regs is a > 4 byte field. [Vitaly] > - Add Reported-by for Kees and Robert since this does technically fix a > build breakage. > - Use a raw literal for NR_EMULATOR_GPRS instead of VCPU_REGS_R15+1 to > play nice with 32-bit builds. [kernel test robot] > - Reduce the number of emulated GPRs to 8 for 32-bit builds. > - Add and use KVM_EMULATOR_BUG_ON() to bug/kill the VM when an emulator > bug is detected. [Vitaly] > > v1: https://lore.kernel.org/all/20220525222604.2810054-1-seanjc@google.com > > Sean Christopherson (8): > KVM: x86: Grab regs_dirty in local 'unsigned long' > KVM: x86: Harden _regs accesses to guard against buggy input > KVM: x86: Omit VCPU_REGS_RIP from emulator's _regs array > KVM: x86: Use 16-bit fields to track dirty/valid emulator GPRs > KVM: x86: Reduce the number of emulator GPRs to '8' for 32-bit KVM > KVM: x86: Bug the VM if the emulator accesses a non-existent GPR > KVM: x86: Bug the VM if the emulator generates a bogus exception > vector > KVM: x86: Bug the VM on an out-of-bounds data read > > arch/x86/kvm/emulate.c | 26 ++++++++++++++++++++------ > arch/x86/kvm/kvm_emulate.h | 28 +++++++++++++++++++++++++--- > arch/x86/kvm/x86.c | 9 +++++++++ > 3 files changed, 54 insertions(+), 9 deletions(-) > > > base-commit: 90bde5bea810d766e7046bf5884f2ccf76dd78e9 > -- > 2.36.1.255.ge46751e96f-goog >