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[23.128.96.18]) by mx.google.com with ESMTP id j1si17287913plr.385.2021.10.18.07.11.36; Mon, 18 Oct 2021 07:11:50 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232201AbhJROLo (ORCPT + 99 others); Mon, 18 Oct 2021 10:11:44 -0400 Received: from mga06.intel.com ([134.134.136.31]:18446 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233877AbhJROLR (ORCPT ); Mon, 18 Oct 2021 10:11:17 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10140"; a="289107350" X-IronPort-AV: E=Sophos;i="5.85,382,1624345200"; d="scan'208";a="289107350" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Oct 2021 07:05:29 -0700 X-IronPort-AV: E=Sophos;i="5.85,382,1624345200"; d="scan'208";a="593822746" Received: from hshariff-mobl.amr.corp.intel.com (HELO [10.212.164.9]) ([10.212.164.9]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Oct 2021 07:05:24 -0700 Subject: Re: [PATCH v8 06/11] x86/traps: Add #VE support for TDX guest To: Borislav Petkov Cc: Kuppuswamy Sathyanarayanan , Thomas Gleixner , Ingo Molnar , x86@kernel.org, Paolo Bonzini , David Hildenbrand , Andrea Arcangeli , Josh Poimboeuf , Juergen Gross , Deep Shah , VMware Inc , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Peter H Anvin , Tony Luck , Dan Williams , Andi Kleen , Kirill Shutemov , Sean Christopherson , Kuppuswamy Sathyanarayanan , linux-kernel@vger.kernel.org References: <20211005025205.1784480-1-sathyanarayanan.kuppuswamy@linux.intel.com> <20211005025205.1784480-7-sathyanarayanan.kuppuswamy@linux.intel.com> <5b7f13b9-6d32-c97c-aaea-4e256a59f90b@intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/18/21 3:53 AM, Borislav Petkov wrote: > On Sun, Oct 17, 2021 at 10:15:22AM -0700, Dave Hansen wrote: >> I think it's equivalent to something like a 'pt_regs' or 'stack_info' >> that we pass around in other exception handlers. It's always stack >> allocated. It's never dynamically allocated and NULL is never passed >> for some other semantic reason. > Ok, but why is adding that check such a big deal? It's really not a big deal. > Are you saying that nothing else will call tdx_get_ve_info() in the > future so we should trust the passed in *ve pointer blindly or should we > simply add that cheap check just in case. > > I don't mind having it without it but wondering why a little defensive > programming is a problem, at all. It's not a problem. I think I'd just rather see a splat (oops or WARN_ON_ONCE()) than silently returning an error.