From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-3465232-1517867067-2-15468560356663351305 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no ("Email failed DMARC policy for domain") X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.001, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='US', FromHeader='com', MailFrom='org' X-Spam-charsets: plain='US-ASCII' X-IgnoreVacation: yes ("Email failed DMARC policy for domain") X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1517867066; b=l8UJj0j+YZEH6ImQ69XHS9gZkInqKotn+nPXux5tbOPGZZC RnRPRsVH/J9FW8tHC2K+5O7nAvg7nEsZ04xK9vj2LSmwyMDm1YSo6wLqCueUnNZx DpHsI7JEOCCjBkr/wAcGs8t7BSyTFtjFFUY5mwI49QcGUDzc2XPeq/3b/4UTg/ik hJGawSGM79Pqq7uuVhbfeGoWMa9GKQCKtoEoGlllguhcWfABYgmiUEYLVAdCShFZ mSyBqpSaqC+Lk5L7ar5i7gRFUbdvifREPd7JZ9275To7Wd/HoGm2uZ8rW1+8wCy4 dBMXW6gLKFkphfanNZ0r5QnMDaIfkSbR1JKhfYw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :in-reply-to:references:mime-version:content-type :content-transfer-encoding:sender:list-id; s=arctest; t= 1517867066; bh=kOJo7Q6ZkNzkadfSvzia+ee0bZzZIg3xsoOvU+RLU30=; b=B 2j27q/4MkEgR9vFiA9krzigJK6IwJB150KTOGDwnq/e6vikM8dTmZI3VjOEE3kuE hYK8GMVkrMZH2+Jqio3hF513NRyTaABUd18XBuLmMRENXwMSS/7mpXUJZfci0eKm WuHqXaiSGBQUyq/cIG8vfIsHfczDQJ89DHLWxXZ+uAkI6xp8IMLkWDEeafH8jdHi aQp1Y2Co7V6IRRaxGbMlpqau8spH5TOp6w6vusfuUYsf+808BWyid3eV4YslfzcS EjOGkwLbKE4xUY1rgdHKKaG3MrMLlVD58hJXDOpDB9FzmMUNjxgnh1NUZT7dwbZn yyBLOtRewXfCg6Arryx1g== ARC-Authentication-Results: i=1; mx4.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=redhat.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=redhat.com header.result=pass header_is_org_domain=yes Authentication-Results: mx4.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=redhat.com; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=redhat.com header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752257AbeBEVoZ (ORCPT ); Mon, 5 Feb 2018 16:44:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:16691 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752010AbeBEVoY (ORCPT ); Mon, 5 Feb 2018 16:44:24 -0500 Date: Mon, 5 Feb 2018 14:44:22 -0700 From: Alex Williamson To: Dan Williams Cc: Haozhong Zhang , Michal Hocko , jack@suse.cz, kvm@vger.kernel.org, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux-fsdevel@vger.kernel.org, hch@lst.de, Subject: Re: [PATCH 3/3] vfio: disable filesystem-dax page pinning Message-ID: <20180205144422.1ca67ab5@w520.home> In-Reply-To: <151778553083.7139.6601964812589807125.stgit@dwillia2-desk3.amr.corp.intel.com> References: <151778551496.7139.17808629759104553625.stgit@dwillia2-desk3.amr.corp.intel.com> <151778553083.7139.6601964812589807125.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Sun, 04 Feb 2018 15:05:30 -0800 Dan Williams wrote: > Filesystem-DAX is incompatible with 'longterm' page pinning. Without > page cache indirection a DAX mapping maps filesystem blocks directly. > This means that the filesystem must not modify a file's block map while > any page in a mapping is pinned. In order to prevent the situation of > userspace holding of filesystem operations indefinitely, disallow > 'longterm' Filesystem-DAX mappings. > > RDMA has the same conflict and the plan there is to add a 'with lease' > mechanism to allow the kernel to notify userspace that the mapping is > being torn down for block-map maintenance. Perhaps something similar can > be put in place for vfio. > > Note that xfs and ext4 still report: > > "DAX enabled. Warning: EXPERIMENTAL, use at your own risk" > > ...at mount time, and resolving the dax-dma-vs-truncate problem is one > of the last hurdles to remove that designation. > > Cc: Alex Williamson > Cc: Michal Hocko > Cc: Christoph Hellwig > Cc: kvm@vger.kernel.org > Cc: > Reported-by: Haozhong Zhang > Fixes: d475c6346a38 ("dax,ext2: replace XIP read and write with DAX I/O") > Signed-off-by: Dan Williams > --- > drivers/vfio/vfio_iommu_type1.c | 18 +++++++++++++++--- > 1 file changed, 15 insertions(+), 3 deletions(-) This isn't without some expense, a vfio mapping and un-mapping unit test incurs ~1.5% increase in system time losing access to gup_fast(). Also, I think tce_iommu_use_page() is going to have the same problem, it provides the same sort of functionality for a different vfio IOMMU backend. Please take this through your tree and I'll add a todo list item to see how we might improve this. Acked-by: Alex Williamson Thanks, Alex > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > index e30e29ae4819..45657e2b1ff7 100644 > --- a/drivers/vfio/vfio_iommu_type1.c > +++ b/drivers/vfio/vfio_iommu_type1.c > @@ -338,11 +338,12 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr, > { > struct page *page[1]; > struct vm_area_struct *vma; > + struct vm_area_struct *vmas[1]; > int ret; > > if (mm == current->mm) { > - ret = get_user_pages_fast(vaddr, 1, !!(prot & IOMMU_WRITE), > - page); > + ret = get_user_pages_longterm(vaddr, 1, !!(prot & IOMMU_WRITE), > + page, vmas); > } else { > unsigned int flags = 0; > > @@ -351,7 +352,18 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr, > > down_read(&mm->mmap_sem); > ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags, page, > - NULL, NULL); > + vmas, NULL); > + /* > + * The lifetime of a vaddr_get_pfn() page pin is > + * userspace-controlled. In the fs-dax case this could > + * lead to indefinite stalls in filesystem operations. > + * Disallow attempts to pin fs-dax pages via this > + * interface. > + */ > + if (ret > 0 && vma_is_fsdax(vmas[0])) { > + ret = -EOPNOTSUPP; > + put_page(page[0]); > + } > up_read(&mm->mmap_sem); > } > >