From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [ARM] Bash often segfaults in Dom0 with the latest Xen Date: Wed, 05 Jun 2013 19:36:00 +0100 Message-ID: <51AF8510.1090907@linaro.org> References: <51AE6DFD.3060308@linaro.org> <51AF25A2.5010207@linaro.org> <51AF6354.4090701@linaro.org> <51AF7B00.5020401@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Christoffer Dall Cc: Andre Przywara , xen-devel , Ian Campbell , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org On 06/05/2013 07:17 PM, Christoffer Dall wrote: > On 5 June 2013 11:01, Stefano Stabellini > wrote: >> On Wed, 5 Jun 2013, Christoffer Dall wrote: >>> On 5 June 2013 10:53, Julien Grall wrote: >>>> On 06/05/2013 06:36 PM, Christoffer Dall wrote: >>>> >>>>>> >>>>>> I'm using the linaro's branch ll_20130528.0, I have only few patches for >>>>>> the dts and not yet in linaro tree patches. >>>>>> >>>>>> I have the same issue with linux 3.9-rc4 with multiple CPUs and I can't >>>>>> really go before without carrying many xen patches to try it. >>>>>> >>>>>> I have tried different configuration with the number of CPUs in Xen >>>>>> (pCPU) and linux (vCPU): >>>>>> - 2 pCPU 2 vCPU : segfaulting >>>>>> - 2 pCPU 1 vCPU : working >>>>>> - 1 pCPU 1 vCPU : working >>>>>> - 1 pCPU 2 vCPU : very slow but working >>>>>> >>>>> 2 pCPU 1 vCPU are you still compiling your dom0 as an SMP kernel, but >>>>> only creating 1 vCPU or are you actually compiling the dom0 as UP? >>>> >>>> >>>> Yes. It's same kernel with the same command line (ie without nosmp). >>>> I have limited the number of dom0 vcpus with dom0_max_vcpus=1 on xen >>>> command line. >>>> >>> It indicates a bug in Xen then. Curious that it only happens for user >>> space in dom0, but perhaps you just haven't seen it in the kernel yet. >>> Bash scripts are pretty intensive on page faults so perhaps there's a >>> synchronization issue with some of your page fault handlers. >>> >>> You could try to touch all the memory inside dom0 (dd to a ramfs for >>> example) and then run your bash script and see if the problem still >>> occurs, that should point you to whether it's a stage-2 fault handling >>> issue, but this is not a fool-proof approach. Maybe Xen can >>> pre-allocate all the stage-2 entries? >> >> Xen pre-allocates all the memory for stage-2 entries (no overcommit or >> populate on demand by default) > > what was the conclusion when pinning the vcpu to dedicated pcpus - did > the error still show up? If I have 2 pCPU (CPU 0 and CPU 2) and 1 vCPU which is moving every 2 second between the pCPUs, Linux will freeze each time the vcpu is running on CPU 1. I'm not sure why, perhaps another issue. As Stefano advised me, I will setup the debugger on the arndale tomorrow and see if I can find something. -- Julien