Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754711AbcK1NRI (ORCPT ); Mon, 28 Nov 2016 08:17:08 -0500 Received: from mx2.suse.de ([195.135.220.15]:35427 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754249AbcK1NRB (ORCPT ); Mon, 28 Nov 2016 08:17:01 -0500 Subject: Re: [PATCH v4] xen/gntdev: Use VM_MIXEDMAP instead of VM_IO to avoid NUMA balancing To: Boris Ostrovsky , david.vrabel@citrix.com References: <1479740166-3109-1-git-send-email-boris.ostrovsky@oracle.com> Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, olaf@aepfle.de, hughd@google.com From: Juergen Gross Message-ID: <9f9eae66-400b-3d08-660f-c0f977ca68e7@suse.com> Date: Mon, 28 Nov 2016 14:16:56 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <1479740166-3109-1-git-send-email-boris.ostrovsky@oracle.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1581 Lines: 55 On 21/11/16 15:56, Boris Ostrovsky wrote: > Commit 9c17d96500f7 ("xen/gntdev: Grant maps should not be subject to > NUMA balancing") set VM_IO flag to prevent grant maps from being > subjected to NUMA balancing. > > It was discovered recently that this flag causes get_user_pages() to > always fail with -EFAULT. > > check_vma_flags > __get_user_pages > __get_user_pages_locked > __get_user_pages_unlocked > get_user_pages_fast > iov_iter_get_pages > dio_refill_pages > do_direct_IO > do_blockdev_direct_IO > do_blockdev_direct_IO > ext4_direct_IO_read > generic_file_read_iter > aio_run_iocb > > (which can happen if guest's vdisk has direct-io-safe option). > > To avoid this let's use VM_MIXEDMAP flag instead --- it prevents > NUMA balancing just as VM_IO does and has no effect on > check_vma_flags(). > > Reported-by: Olaf Hering > Suggested-by: Hugh Dickins > Signed-off-by: Boris Ostrovsky Applied to xen/tip.git for-linus-4.10 Juergen > --- > drivers/xen/gntdev.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c > index bb95212..2ef2b61 100644 > --- a/drivers/xen/gntdev.c > +++ b/drivers/xen/gntdev.c > @@ -1007,7 +1007,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma) > > vma->vm_ops = &gntdev_vmops; > > - vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_IO; > + vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_MIXEDMAP; > > if (use_ptemod) > vma->vm_flags |= VM_DONTCOPY; >