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 X-Spam-Level: X-Spam-Status: No, score=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8ACFCC433DB for ; Fri, 12 Mar 2021 20:59:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 55AB664F87 for ; Fri, 12 Mar 2021 20:59:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235114AbhCLU7J (ORCPT ); Fri, 12 Mar 2021 15:59:09 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:50946 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235079AbhCLU6z (ORCPT ); Fri, 12 Mar 2021 15:58:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615582734; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tqrwGSWs78kmFc+bZgFNWuIXo+lT3T9Q8DDXoclb0G4=; b=jBZSQEZ2l3aVpNqcDfR6cXl6+vOPcrraFOzJHNZMMByYd0UoF6uFFF4BETKVfi3z8eDrVq RuDvOIOGY76gRlSktoCCviP3OCJK0XxnoThyxlAxFkfZG1eebWx0YxK2HZs+PTI5yjMbtb bwDkJP31QjYnj9DXXLIQQZhWA4zdJ9E= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-553-nJHOhb7fOK239aU1O3cm5A-1; Fri, 12 Mar 2021 15:58:51 -0500 X-MC-Unique: nJHOhb7fOK239aU1O3cm5A-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 763838189C7; Fri, 12 Mar 2021 20:58:49 +0000 (UTC) Received: from omen.home.shazbot.org (ovpn-112-255.phx2.redhat.com [10.3.112.255]) by smtp.corp.redhat.com (Postfix) with ESMTP id E57FF5D9CC; Fri, 12 Mar 2021 20:58:44 +0000 (UTC) Date: Fri, 12 Mar 2021 13:58:44 -0700 From: Alex Williamson To: Jason Gunthorpe Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, peterx@redhat.com, prime.zeng@hisilicon.com, cohuck@redhat.com Subject: Re: [PATCH] vfio/pci: Handle concurrent vma faults Message-ID: <20210312135844.5e97aac7@omen.home.shazbot.org> In-Reply-To: <20210312130938.1e535e50@omen.home.shazbot.org> References: <161539852724.8302.17137130175894127401.stgit@gimli.home> <20210310181446.GZ2356281@nvidia.com> <20210310113406.6f029fcf@omen.home.shazbot.org> <20210310184011.GA2356281@nvidia.com> <20210312121611.07a313e3@omen.home.shazbot.org> <20210312194147.GH2356281@nvidia.com> <20210312130938.1e535e50@omen.home.shazbot.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, 12 Mar 2021 13:09:38 -0700 Alex Williamson wrote: > On Fri, 12 Mar 2021 15:41:47 -0400 > Jason Gunthorpe wrote: > > > ====================================================== > WARNING: possible circular locking dependency detected > 5.12.0-rc1+ #18 Not tainted > ------------------------------------------------------ > CPU 0/KVM/1406 is trying to acquire lock: > ffffffffa5a58d60 (fs_reclaim){+.+.}-{0:0}, at: fs_reclaim_acquire+0x83/0xd0 > > but task is already holding lock: > ffff94c0f3e8fb08 (&mapping->i_mmap_rwsem){++++}-{3:3}, at: vfio_device_io_remap_mapping_range+0x31/0x120 [vfio] > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #1 (&mapping->i_mmap_rwsem){++++}-{3:3}: > down_write+0x3d/0x70 > dma_resv_lockdep+0x1b0/0x298 > do_one_initcall+0x5b/0x2d0 > kernel_init_freeable+0x251/0x298 > kernel_init+0xa/0x111 > ret_from_fork+0x22/0x30 > > -> #0 (fs_reclaim){+.+.}-{0:0}: > __lock_acquire+0x111f/0x1e10 > lock_acquire+0xb5/0x380 > fs_reclaim_acquire+0xa3/0xd0 > kmem_cache_alloc_trace+0x30/0x2c0 > memtype_reserve+0xc3/0x280 > reserve_pfn_range+0x86/0x160 > track_pfn_remap+0xa6/0xe0 > remap_pfn_range+0xa8/0x610 > vfio_device_io_remap_mapping_range+0x93/0x120 [vfio] > vfio_pci_test_and_up_write_memory_lock+0x34/0x40 [vfio_pci] > vfio_basic_config_write+0x12d/0x230 [vfio_pci] > vfio_pci_config_rw+0x1b7/0x3a0 [vfio_pci] > vfs_write+0xea/0x390 > __x64_sys_pwrite64+0x72/0xb0 > do_syscall_64+0x33/0x40 > entry_SYSCALL_64_after_hwframe+0x44/0xae > .. > > Does current_gfp_context()/memalloc_nofs_save()/etc solve it? Yeah, we can indeed use memalloc_nofs_save/restore(). It seems we're trying to allocate something for pfnmap tracking and that enables lots of lockdep specific tests. Is it valid to wrap io_remap_pfn_range() around clearing this flag or am I just masking a bug? Thanks, Alex