From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH 02/18] KVM: MMU: Make tdp_enabled a mmu-context parameter Date: Wed, 10 Mar 2010 16:26:43 +0100 Message-ID: <20100310152643.GO5619@amd.com> References: <1267643541-451-1-git-send-email-joerg.roedel@amd.com> <1267643541-451-3-git-send-email-joerg.roedel@amd.com> <4B94C0B5.7080507@redhat.com> <20100310144426.GK5619@amd.com> <4B97B269.3010502@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: Marcelo Tosatti , Alexander Graf , kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Avi Kivity Return-path: Received: from tx2ehsobe001.messaging.microsoft.com ([65.55.88.11]:36166 "EHLO TX2EHSOBE002.bigfish.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756034Ab0CJP06 (ORCPT ); Wed, 10 Mar 2010 10:26:58 -0500 Content-Disposition: inline In-Reply-To: <4B97B269.3010502@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Mar 10, 2010 at 04:53:29PM +0200, Avi Kivity wrote: > On 03/10/2010 04:44 PM, Joerg Roedel wrote: > >On Mon, Mar 08, 2010 at 11:17:41AM +0200, Avi Kivity wrote: > >>On 03/03/2010 09:12 PM, Joerg Roedel wrote: > >>>This patch changes the tdp_enabled flag from its global > >>>meaning to the mmu-context. This is necessary for Nested SVM > >>>with emulation of Nested Paging where we need an extra MMU > >>>context to shadow the Nested Nested Page Table. > >>> > >>> > >>>diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > >>>index ec891a2..e7bef19 100644 > >>>--- a/arch/x86/include/asm/kvm_host.h > >>>+++ b/arch/x86/include/asm/kvm_host.h > >>>@@ -254,6 +254,7 @@ struct kvm_mmu { > >>> int root_level; > >>> int shadow_root_level; > >>> union kvm_mmu_page_role base_role; > >>>+ bool tdp_enabled; > >>> > >>This needs a different name, since the old one is still around. > >>Perhaps we could call it parent_mmu and make it a kvm_mmu pointer. > >Hmm, how about renaming the global tdp_enabled variable to tdp_usable? > >The global variable indicates if tdp is _usable_ and we can _enable_ it > >for a mmu context. > > I think of the global flags as host tdp, and the mmu as guest tdp > (but maybe this is wrong?). If that makes sense, the naming should > reflect that. The basic flow of the mmu state with npt-npt is: 1. As long as the L1 is running the arch.mmu context is in tdp mode and builds a direct-mapped page table. 2. When vmrun is emulated and the nested vmcb enables nested paging, arch.mmu is switched to a shadow-mmu mode which now shadows the l1 nested page table. So when the l2-guest runs with nested paging the arch.mmu.tdp_enabled variable on the host is false. 3. On a vmexit emulation the mmu is switched back to tdp handling state. So the mmu.tdp_enabled parameter is about tdp being enabled for the mmu context (so mmu.tdp_enabled means that we build a l1-direct-mapped page table when true or shadow a l1-page-table when false). Thats why I think the 'tdp_enabled' name makes sense in the mmu-context. The global flag only shows if an mmu-context could be in tdp-state. So tdp_usable may be a good name for it. Joerg