From mboxrd@z Thu Jan 1 00:00:00 1970 From: Razvan Cojocaru Subject: Re: Failed vm entry with heavy use of emulator Date: Tue, 5 Jan 2016 14:35:11 +0200 Message-ID: <568BB87F.7000207@bitdefender.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1aGQoE-00011U-S0 for xen-devel@lists.xenproject.org; Tue, 05 Jan 2016 12:33:54 +0000 Received: from smtp01.buh.bitdefender.com (unknown [10.17.80.75]) by mx-sr.buh.bitdefender.com (Postfix) with ESMTP id 80304800CC for ; Tue, 5 Jan 2016 14:33:51 +0200 (EET) 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: Tamas K Lengyel , Xen-devel List-Id: xen-devel@lists.xenproject.org On 01/05/2016 01:49 PM, Tamas K Lengyel wrote: > Hi all, > I've been stress-testing the built-in emulator using the vm_event > response VM_EVENT_FLAG_EMULATE feature. In the test I've turned all > pages non-readable by default and all trapped instructions to be > emulated. My test code can be found at > https://github.com/tklengyel/xen/compare/read_emul?expand=1. > > The following crash is reproducible and has been verified by Razvan as well. Indeed, but I should point out that it only occurs when all the pages are not readable. For all other cases (restricting write or execute, that have been heavily tested here) there seem to be no issues, regardless of how hard we're driving the emulator. Tamas found this strange (and I agree) since we've assumed that the emulator doesn't care about EPT restrictions. But our use cases so far have never blocked page reads. Cheers, Razvan