From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH 3/4] kvm, memory-hotplug: Update ept identity pagetable when it is migrated. Date: Fri, 4 Jul 2014 12:49:50 +0300 Message-ID: <20140704094949.GD4399@minantech.com> References: <1404291637-15048-1-git-send-email-tangchen@cn.fujitsu.com> <1404291637-15048-4-git-send-email-tangchen@cn.fujitsu.com> <20140702163420.GC4399@minantech.com> <53B61316.2050208@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: mtosatti@redhat.com, kvm@vger.kernel.org, laijs@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, guz.fnst@cn.fujitsu.com, linux-kernel@vger.kernel.org To: Tang Chen Return-path: Content-Disposition: inline In-Reply-To: <53B61316.2050208@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Fri, Jul 04, 2014 at 10:36:06AM +0800, Tang Chen wrote: > Hi Gleb, > > On 07/03/2014 12:34 AM, Gleb Natapov wrote: > >On Wed, Jul 02, 2014 at 05:00:36PM +0800, Tang Chen wrote: > >>ept identity pagetable is pinned in memory, and as a result it cannot be > >>migrated/hot-removed. > >> > >>But actually it doesn't need to be pinned in memory. > >> > >>This patch introduces a new vcpu request: KVM_REQ_MIGRATE_EPT to reset ept > >>indetity pagetable related variable. This request will be made when > >>kvm_mmu_notifier_invalidate_page() is called when the page is unmapped > >>from the qemu user space to reset kvm->arch.ept_identity_pagetable to NULL. > >>And will also be made when ept violation happens to reset > >>kvm->arch.ept_identity_pagetable to the new page. > > > >kvm->arch.ept_identity_pagetable is never used as a page address, just > >boolean null/!null to see if identity pagetable is initialized. I do > >not see why would we want to track its address at all. Changing it to bool > >and assigning true during initialization should be enough. > > We already have kvm->arch.ept_identity_pagetable_done to indicate if the ept > identity table is initialized. If we make kvm->arch.ept_identity_pagetable > to > bool, do you mean we have: > > kvm->arch.ept_identity_pagetable: indicate if ept page is allocated, > kvm->arch.ept_identity_pagetable_done: indicate if ept page is initialized ? > ept_identity_pagetable also means that a memory slot for identity page is initialized. > I don't think we need this. Shall we remove kvm->arch.ept_identity_pagetable > ? > May be those two can be consolidated somehow, but lets leave it to a separate patch to make this one simpler. -- Gleb.