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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 114DAC43144 for ; Thu, 28 Jun 2018 10:21:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C1EEE24B92 for ; Thu, 28 Jun 2018 10:21:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C1EEE24B92 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=hisilicon.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753269AbeF1KVH (ORCPT ); Thu, 28 Jun 2018 06:21:07 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:9130 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751519AbeF1KVE (ORCPT ); Thu, 28 Jun 2018 06:21:04 -0400 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 074757D8705ED; Thu, 28 Jun 2018 18:20:51 +0800 (CST) Received: from [127.0.0.1] (10.202.226.42) by DGGEMS406-HUB.china.huawei.com (10.3.19.206) with Microsoft SMTP Server id 14.3.382.0; Thu, 28 Jun 2018 18:20:43 +0800 Subject: Re: KVM guest sometimes failed to boot because of kernel stack overflow if KPTI is enabled on a hisilicon ARM64 platform. To: James Morse References: <5B2A6218.3030201@hisilicon.com> <20180620144257.GB27776@arm.com> <5B2A7832.4010502@hisilicon.com> <5B2A7FE1.5040607@hisilicon.com> <5B2B6DEA.2090100@hisilicon.com> <5B3274FC.7000206@hisilicon.com> <20180626174746.GO23375@arm.com> <942e76b6-a46a-6c5e-5ec3-67daca636d43@arm.com> <5B339068.5020304@hisilicon.com> <9549e15d-4ec6-8dd3-2237-b6c9b52fc816@arm.com> CC: Will Deacon , , , Linuxarm , Zhangyi ac , , , "Xiongfanggou (James)" , , , , "Liyuan (Larry, Turing Solution)" , From: Wei Xu Message-ID: <5B34B673.20803@hisilicon.com> Date: Thu, 28 Jun 2018 11:20:35 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <9549e15d-4ec6-8dd3-2237-b6c9b52fc816@arm.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.226.42] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi James, On 2018/6/28 9:45, James Morse wrote: > Hi Wei, > > On 27/06/18 14:26, Wei Xu wrote: >> Sorry, I should highlight that I have only updated the default value >> of CONFIG_NR_CPUS by menuconfig in the previous mail. >> That is why it showed dirty. > > (menuconfig changes don't show up like this) Thanks! Sorry, yes, you are right. I did not see dirty after I reset the proc.S. > > > More than 64 CPUs ... Is this system running more VMs than it has VMIDs? Too-few > VMIDs does work with KVM, its just going to trigger rollover frequently. > No, we just ran one VM. > Just to check, what kernel version is the host running? Does it have commit > f0cf47d939d0 ("KVM: arm/arm64: Close VMID generation race") > (looks like that went in as a fix for v4.17-rc3) Yes, the host is runing 4.18-rc2 as the guest including above commit. > > Are you running (lots) of other VMs whenever this happens? Do they have multiple > vcpus? (I'm thinking of the scenario in that patch's description) No, we just ran one VM with 1 cpu. > > Is the host system otherwise idle when this happens? > (If not, can you reproduce the issue without exhausting the VMIDs?) > > > It may be that writing back the page-table entries with the MMU off, and > changing the cache maintenance are just changing the timing of something else. > Yes, maybe. Now we are debugging with the SoC guys together. Thanks! Best Regards, Wei > > Thanks, > > James > > . >