From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v8 13/15] ARM: KVM: Handle guest faults in KVM Date: Tue, 19 Jun 2012 12:32:06 +0300 Message-ID: <4FE04716.6090202@redhat.com> References: <20120615190553.24590.18391.stgit@ubuntu> <20120615190908.24590.95861.stgit@ubuntu> <4FDF30E3.5040506@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: android-virt@lists.cs.columbia.edu, kvm@vger.kernel.org, Andrea Arcangeli , Marc Zyngier To: Christoffer Dall Return-path: Received: from mx1.redhat.com ([209.132.183.28]:17868 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751058Ab2FSJcT (ORCPT ); Tue, 19 Jun 2012 05:32:19 -0400 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On 06/19/2012 01:20 AM, Christoffer Dall wrote: > On Mon, Jun 18, 2012 at 9:45 AM, Avi Kivity wrote: >> On 06/15/2012 10:09 PM, Christoffer Dall wrote: >>> From: Christoffer Dall >>> >>> Handles the guest faults in KVM by mapping in corresponding user pages >>> in the 2nd stage page tables. >>> >>> Introduces new ARM-specific kernel memory types, PAGE_KVM_GUEST and >>> pgprot_guest variables used to map 2nd stage memory for KVM guests. >>> >>> Leverages MMU notifiers on KVM/ARM by supporting the kvm_unmap_hva() operation, >>> where we remove the HVA from the 2nd stage translation. All other KVM MMU >>> notifierhooks are NOPs. >> >> I think you must at least support change_pte (possibly by unmapping). >> Andrea? >> > hmmm, at least for KSM support we need to support change_pte (are > there other callers for this type of memory?) > > It's not trivial I guess, since we would need to support COW and > thereby stage-2 permission faults... Marc, right? As I mentioned, you can support change_pte by unmapping. This will cause ksm to be ineffective (pages will only be shared if the guest doesn't touch them at all), but it's enough to get started. -- error compiling committee.c: too many arguments to function