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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 900D5C433F5 for ; Wed, 5 Jan 2022 06:07:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EF36D6B0071; Wed, 5 Jan 2022 01:07:49 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id EA22D6B0073; Wed, 5 Jan 2022 01:07:49 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D6AAF6B0074; Wed, 5 Jan 2022 01:07:49 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0100.hostedemail.com [216.40.44.100]) by kanga.kvack.org (Postfix) with ESMTP id C792A6B0071 for ; Wed, 5 Jan 2022 01:07:49 -0500 (EST) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 63F21181CB153 for ; Wed, 5 Jan 2022 06:07:49 +0000 (UTC) X-FDA: 78995202258.30.614859F Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by imf28.hostedemail.com (Postfix) with ESMTP id 12AD9C000F for ; Wed, 5 Jan 2022 06:07:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1641362868; x=1672898868; h=date:from:to:cc:subject:message-id:reply-to:references: mime-version:in-reply-to; bh=07p9MpW9zMg9Qp6lAa6OCqWxIJ+2lO0bV8d8+HqWdzA=; b=N8St6t4KL+FgrQRqk0+vw48zfmHwaRaK1m/w88HrRXGuh61uPFZeCFpW JDRbw+w/VTiYjt5iq4a7u/V8slRUh+vCl7IOO5N7nCvca7UqAGEGjrcoa 1uxIidTbeBZNiEMr1HrXkeRdXkjj2pKsaw0l9lh3NRQPg2nVNE3F/qfxV HMUGBdR3xWKQ6c/NGDgg4v86EY9LU7DR0nuz6yl7m/MiUvzt0rLqWsWCX 8E5CN5KXTyxZp5izc3UweV1FGalgYXsz4Je2QWEa4HWIRu8gI42m1kLcY ZvFT8+zDLhtLdVG4PjA1DKKbkysk4+XyWO3VTJvDTC1IL3bj0ktzApl3n g==; X-IronPort-AV: E=McAfee;i="6200,9189,10217"; a="239917575" X-IronPort-AV: E=Sophos;i="5.88,262,1635231600"; d="scan'208";a="239917575" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Jan 2022 22:07:45 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,262,1635231600"; d="scan'208";a="526379627" Received: from chaop.bj.intel.com (HELO localhost) ([10.240.192.101]) by orsmga008.jf.intel.com with ESMTP; 04 Jan 2022 22:07:38 -0800 Date: Wed, 5 Jan 2022 14:07:04 +0800 From: Chao Peng To: Sean Christopherson Cc: Robert Hoo , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, qemu-devel@nongnu.org, Paolo Bonzini , Jonathan Corbet , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Yu Zhang , "Kirill A . Shutemov" , luto@kernel.org, john.ji@intel.com, susie.li@intel.com, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com Subject: Re: [PATCH v3 kvm/queue 03/16] mm/memfd: Introduce MEMFD_OPS Message-ID: <20220105060704.GA25009@chaop.bj.intel.com> Reply-To: Chao Peng References: <20211223123011.41044-1-chao.p.peng@linux.intel.com> <20211223123011.41044-4-chao.p.peng@linux.intel.com> <95d13ac7da32aa1530d6883777ef3279e4ad825d.camel@linux.intel.com> <20211231023853.GB7255@chaop.bj.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=N8St6t4K; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf28.hostedemail.com: domain of chao.p.peng@linux.intel.com has no SPF policy when checking 192.55.52.93) smtp.mailfrom=chao.p.peng@linux.intel.com X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 12AD9C000F X-Stat-Signature: sz7kmk159zrwrsoxcdwniif5xzu8xkdg X-HE-Tag: 1641362867-815143 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jan 04, 2022 at 05:38:38PM +0000, Sean Christopherson wrote: > On Fri, Dec 31, 2021, Chao Peng wrote: > > On Fri, Dec 24, 2021 at 11:53:15AM +0800, Robert Hoo wrote: > > > On Thu, 2021-12-23 at 20:29 +0800, Chao Peng wrote: > > > > From: "Kirill A. Shutemov" > > > > > > > > +static void notify_fallocate(struct inode *inode, pgoff_t start, > > > > pgoff_t end) > > > > +{ > > > > +#ifdef CONFIG_MEMFD_OPS > > > > + struct shmem_inode_info *info = SHMEM_I(inode); > > > > + const struct memfd_falloc_notifier *notifier; > > > > + void *owner; > > > > + bool ret; > > > > + > > > > + if (!info->falloc_notifier) > > > > + return; > > > > + > > > > + spin_lock(&info->lock); > > > > + notifier = info->falloc_notifier; > > > > + if (!notifier) { > > > > + spin_unlock(&info->lock); > > > > + return; > > > > + } > > > > + > > > > + owner = info->owner; > > > > + ret = notifier->get_owner(owner); > > > > + spin_unlock(&info->lock); > > > > + if (!ret) > > > > + return; > > > > + > > > > + notifier->fallocate(inode, owner, start, end); > > > > > > I see notifier->fallocate(), i.e. memfd_fallocate(), discards > > > kvm_memfd_fallocate_range()'s return value. Should it be checked? > > > > I think we can ignore it, just like how current mmu_notifier does, > > the return value of __kvm_handle_hva_range is discarded in > > kvm_mmu_notifier_invalidate_range_start(). Even when KVM side failed, > > it's not fatal, it should not block the operation in the primary MMU. > > If the return value is ignored, it'd be better to have no return value at all so > that it's clear fallocate() will continue on regardless of whether or not the > secondary MMU callback succeeds. E.g. if KVM can't handle the fallocate() for > whatever reason, then knowing that fallocate() will continue on means KVM should > mark the VM as dead so that the broken setup cannot be abused by userspace. After a close look, kvm_unmap_gfn_range() actually does not return a error code, so it's safe to not return in kvm_memfd_handle_range(). Chao