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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C910AC4332F for ; Thu, 2 Nov 2023 02:21:07 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=bte/I6DS; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4SLSKZ1JYwz3cYw for ; Thu, 2 Nov 2023 13:21:06 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=bte/I6DS; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=intel.com (client-ip=134.134.136.126; helo=mgamail.intel.com; envelope-from=xiaoyao.li@intel.com; receiver=lists.ozlabs.org) Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.126]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4SLSJX0m84z2xdp for ; Thu, 2 Nov 2023 13:20:08 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1698891612; x=1730427612; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=qMSrBq5gKSfvneC99jG0ycqZi9wUzkwKrG5m2lwT0dM=; b=bte/I6DSDgFiVG2RZfA7jgi9mG9JaWTM3P/Tuge2EaYLnoLj8wkimcXy kWe7ZXX4m8u63Pr6r8j/4Ie8jPNmoHCUTw5OLr81L92XEGNr4sr6rvMfW oPHp86/AZDq5TuTd40DSZy5q5WiVBNB5neo92fP+Gww/dqMyZ7lqP1hcW F7ara6AJsqaKPl0O0ytxRAFuIneDpDHC+XVYXPKYzpXbir9MsgS1J5++7 NtpyDplzQF5IpD51+5D6/VKzHxkKDphGaxmKRBg7l6oXe+YJ9Ly0ka3cI WZUBg8gozjOwXz+5CreQlUVJt5yAt6Hn2xGEz87BAxp6VyyhO2D/BWOfR g==; X-IronPort-AV: E=McAfee;i="6600,9927,10881"; a="373665332" X-IronPort-AV: E=Sophos;i="6.03,270,1694761200"; d="scan'208";a="373665332" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Nov 2023 19:20:04 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10881"; a="851761891" X-IronPort-AV: E=Sophos;i="6.03,270,1694761200"; d="scan'208";a="851761891" Received: from xiaoyaol-hp-g830.ccr.corp.intel.com (HELO [10.93.9.145]) ([10.93.9.145]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Nov 2023 19:19:53 -0700 Message-ID: <33686031-c1df-4ef5-a6ac-1aab7f5c656e@intel.com> Date: Thu, 2 Nov 2023 10:19:50 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v13 09/35] KVM: Add KVM_EXIT_MEMORY_FAULT exit to report faults to userspace Content-Language: en-US To: Sean Christopherson , Kai Huang References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-10-seanjc@google.com> <482bfea6f54ea1bb7d1ad75e03541d0ba0e5be6f.camel@intel.com> From: Xiaoyao Li In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "kvm@vger.kernel.org" , "david@redhat.com" , "linux-mips@vger.kernel.org" , "linux-mm@kvack.org" , "kvmarm@lists.linux.dev" , "pbonzini@redhat.com" , "chao.p.peng@linux.intel.com" , "linux-riscv@lists.infradead.org" , "isaku.yamahata@gmail.com" , "chenhuacai@kernel.org" , "willy@infradead.org" , Wei W Wang , "vbabka@suse.cz" , "yu.c.zhang@linux.intel.com" , "linux-arm-kernel@lists.infradead.org" , "mail@maciej.szmigiero.name" , "aou@eecs.berkeley.edu" , "michael.roth@amd.com" , "ackerleytng@google.com" , "viro@zeniv.linux.o rg.uk" , "paul.walmsley@sifive.com" , "mic@digikod.net" , "tabba@google.com" , Isaku Yamahata , "brauner@kernel.org" , "qperret@google.com" , "anup@brainfault.org" , "linux-kernel@vger.kernel.org" , "oliver.upton@linux.dev" , "dmatlack@google.com" , "jarkko@kernel.org" , "palmer@dabbelt.com" , "amoorthy@google.com" , "kvm-riscv@lists.infradead.org" , "maz@kernel.org" , "linux-fsdevel@vger.kernel.org" , "liam.merwick@oracle.com" , "akpm@linux-foundation.org" , Vishal Annapurve , "linuxppc-dev@lists.ozlabs.org" , Yilun Xu , "kirill.shutemov@linux.intel.com" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 11/2/2023 1:36 AM, Sean Christopherson wrote: >> KVM_CAP_MEMORY_FAULT_INFO is x86 only, is it better to put this function to >> ? > I'd prefer to keep it in generic code, as it's highly likely to end up there > sooner than later. There's a known use case for ARM (exit to userspace on missing > userspace mapping[*]), and I'm guessing pKVM (also ARM) will also utilize this API. > > [*]https://lore.kernel.org/all/20230908222905.1321305-8-amoorthy@google.com I wonder how this CAP is supposed to be checked in userspace, for guest memfd case? something like this? if (!kvm_check_extension(s, KVM_CAP_MEMORY_FAULT_INFO) && run->exit_reason == KVM_EXIT_MEMORY_FAULT) abort("unexpected KVM_EXIT_MEMORY_FAULT"); In my implementation of QEMU patches, I find it's unnecessary. When userspace gets an exit with KVM_EXIT_MEMORY_FAULT, it implies "KVM_CAP_MEMORY_FAULT_INFO". So I don't see how it is necessary in this series. Whether it's necessary or not for [*], I don't have the answer but we can leave the discussion to that patch series.