From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefano Stabellini Subject: Re: [ARM] Bash often segfaults in Dom0 with the latest Xen Date: Wed, 5 Jun 2013 19:01:05 +0100 Message-ID: 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 , Julien Grall , Ian Campbell , Stefano Stabellini , xen-devel List-Id: xen-devel@lists.xenproject.org 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)