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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 4F1B3C04E87 for ; Mon, 20 May 2019 21:36:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2D8CF21479 for ; Mon, 20 May 2019 21:36:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726566AbfETVg5 (ORCPT ); Mon, 20 May 2019 17:36:57 -0400 Received: from mx2.cyber.ee ([193.40.6.72]:49338 "EHLO mx2.cyber.ee" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725776AbfETVg4 (ORCPT ); Mon, 20 May 2019 17:36:56 -0400 Subject: Re: [PATCH v2] vmalloc: Fix issues with flush flag To: Rick Edgecombe , linux-kernel@vger.kernel.org, peterz@infradead.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org Cc: dave.hansen@intel.com, namit@vmware.com, Meelis Roos , "David S. Miller" , Borislav Petkov , Andy Lutomirski , Ingo Molnar References: <20190520200703.15997-1-rick.p.edgecombe@intel.com> From: Meelis Roos Message-ID: <90f8a4e1-aa71-0c10-1a91-495ba0cb329b@linux.ee> Date: Tue, 21 May 2019 00:36:22 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190520200703.15997-1-rick.p.edgecombe@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: et-EE Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Switch VM_FLUSH_RESET_PERMS to use a regular TLB flush intead of > vm_unmap_aliases() and fix calculation of the direct map for the > CONFIG_ARCH_HAS_SET_DIRECT_MAP case. > > Meelis Roos reported issues with the new VM_FLUSH_RESET_PERMS flag on a > sparc machine. On investigation some issues were noticed: > > 1. The calculation of the direct map address range to flush was wrong. > This could cause problems on x86 if a RO direct map alias ever got loaded > into the TLB. This shouldn't normally happen, but it could cause the > permissions to remain RO on the direct map alias, and then the page > would return from the page allocator to some other component as RO and > cause a crash. > > 2. Calling vm_unmap_alias() on vfree could potentially be a lot of work to > do on a free operation. Simply flushing the TLB instead of the whole > vm_unmap_alias() operation makes the frees faster and pushes the heavy > work to happen on allocation where it would be more expected. > In addition to the extra work, vm_unmap_alias() takes some locks including > a long hold of vmap_purge_lock, which will make all other > VM_FLUSH_RESET_PERMS vfrees wait while the purge operation happens. > > 3. page_address() can have locking on some configurations, so skip calling > this when possible to further speed this up. > > Fixes: 868b104d7379 ("mm/vmalloc: Add flag for freeing of special permsissions") > Reported-by: Meelis Roos > Cc: Meelis Roos > Cc: Peter Zijlstra > Cc: "David S. Miller" > Cc: Dave Hansen > Cc: Borislav Petkov > Cc: Andy Lutomirski > Cc: Ingo Molnar > Cc: Nadav Amit > Signed-off-by: Rick Edgecombe > --- > > Changes since v1: > - Update commit message with more detail > - Fix flush end range on !CONFIG_ARCH_HAS_SET_DIRECT_MAP case It does not work on my V445 where the initial problem happened. [ 46.582633] systemd[1]: Detected architecture sparc64. Welcome to Debian GNU/Linux 10 (buster)! [ 46.759048] systemd[1]: Set hostname to . [ 46.831383] systemd[1]: Failed to bump fs.file-max, ignoring: Invalid argument [ 67.989695] rcu: INFO: rcu_sched detected stalls on CPUs/tasks: [ 68.074706] rcu: 0-...!: (0 ticks this GP) idle=5c6/1/0x4000000000000000 softirq=33/33 fqs=0 [ 68.198443] rcu: 2-...!: (0 ticks this GP) idle=e7e/1/0x4000000000000000 softirq=67/67 fqs=0 [ 68.322198] (detected by 1, t=5252 jiffies, g=-939, q=108) [ 68.402204] CPU[ 0]: TSTATE[0000000080001603] TPC[000000000043f298] TNPC[000000000043f29c] TASK[systemd-debug-g:89] [ 68.556001] TPC[smp_synchronize_tick_client+0x18/0x1a0] O7[0xfff000010000691c] I7[xcall_sync_tick+0x1c/0x2c] RPC[alloc_set_pte+0xf4/0x300] [ 68.750973] CPU[ 2]: TSTATE[0000000080001600] TPC[000000000043f298] TNPC[000000000043f29c] TASK[systemd-cryptse:88] [ 68.904741] TPC[smp_synchronize_tick_client+0x18/0x1a0] O7[filemap_map_pages+0x3cc/0x3e0] I7[xcall_sync_tick+0x1c/0x2c] RPC[handle_mm_fault+0xa0/0x180] [ 69.115991] rcu: rcu_sched kthread starved for 5252 jiffies! g-939 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=3 [ 69.262239] rcu: RCU grace-period kthread stack dump: [ 69.334741] rcu_sched I 0 10 2 0x06000000 [ 69.413495] Call Trace: [ 69.448501] [000000000093325c] schedule+0x1c/0xc0 [ 69.517253] [0000000000936c74] schedule_timeout+0x154/0x260 [ 69.598514] [00000000004b65a4] rcu_gp_kthread+0x4e4/0xac0 [ 69.677261] [000000000047ecfc] kthread+0xfc/0x120 [ 69.746018] [00000000004060a4] ret_from_fork+0x1c/0x2c [ 69.821014] [0000000000000000] 0x0 and hangs here, software watchdog kicks in soon. -- Meelis Roos