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 4A5EAC1975A for ; Wed, 25 Mar 2020 16:46:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 25F9E2073E for ; Wed, 25 Mar 2020 16:46:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727491AbgCYQqH (ORCPT ); Wed, 25 Mar 2020 12:46:07 -0400 Received: from mga18.intel.com ([134.134.136.126]:16645 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725812AbgCYQqH (ORCPT ); Wed, 25 Mar 2020 12:46:07 -0400 IronPort-SDR: eiRnF4iyvQgPW3HA1lercI1DGJGCF/VwJ56oxE+KfCOiShOBA/Q1ABcCKxEMCXE584i3bYYfno 5xmQYlDXgx6g== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2020 09:46:06 -0700 IronPort-SDR: qU1+J/5Xox6TbQ+ZX2geXP9optmei7F66ixyPp1LlBWwXIpiZlRRCRXlyi5NklfKeADMO2qB0I vDEcVGULOcNA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,304,1580803200"; d="scan'208";a="250461208" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.202]) by orsmga006.jf.intel.com with ESMTP; 25 Mar 2020 09:46:06 -0700 Date: Wed, 25 Mar 2020 09:46:06 -0700 From: Sean Christopherson To: Paolo Bonzini Cc: Randy Dunlap , Stephen Rothwell , Linux Next Mailing List , Linux Kernel Mailing List , KVM , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Subject: Re: linux-next: Tree for Mar 25 (arch/x86/kvm/) Message-ID: <20200325164606.GH14294@linux.intel.com> References: <20200325195350.7300fee9@canb.auug.org.au> <064720eb-2147-1b92-7a62-f89d6380f40a@infradead.org> <85430f7e-93e0-3652-0705-9cf6e948a9d8@redhat.com> <20200325161405.GG14294@linux.intel.com> <7b71119b-4594-2535-24ba-2c59430e4f30@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7b71119b-4594-2535-24ba-2c59430e4f30@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-next-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-next@vger.kernel.org On Wed, Mar 25, 2020 at 05:26:20PM +0100, Paolo Bonzini wrote: > On 25/03/20 17:14, Sean Christopherson wrote: > >> Doh, right. I think the only solution for that one is to degrade it to > >> WARN_ON(1). > > I reproduced the error, give me a bit to play with the code to see if the > > BUILD_BUG can be preserved. I'm curious as to why kvm_cpu_cap_mask() is > > special, and why it only fails with this config. > > > > I could not reproduce it, but I would not be surprised if there are > other configurations where the compiler cannot constant-propagate from > the reverse_cpuid struct into __cpuid_entry_get_reg. The error is related to UBSAN. There is at least one legitimate (but benign) underlying issue. I'm chasing down a second instance of the BUILD_BUG. Assuming all issues can be fixed, I think it'd make sense to keep the BUILD_BUG, especially if it's teasing out actual weirdness, even if the weirdness is benign.