From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [Patch v4 2/4] Add SMEP handling when setting CR4 Date: Wed, 1 Jun 2011 09:32:03 -0300 Message-ID: <20110601123203.GA2429@amt.cnet> References: <5D8008F58939784290FAB48F5497519844E9278011@shsmsx502.ccr.corp.intel.com> <20110531175232.GA2721@amt.cnet> <4DE52DEF.2000009@redhat.com> <20110531184827.GA4376@amt.cnet> <4DE53B7E.4070403@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Yang, Wei Y" , "kvm@vger.kernel.org" To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:27154 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755938Ab1FAMcm (ORCPT ); Wed, 1 Jun 2011 08:32:42 -0400 Content-Disposition: inline In-Reply-To: <4DE53B7E.4070403@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, May 31, 2011 at 10:03:26PM +0300, Avi Kivity wrote: > On 05/31/2011 09:48 PM, Marcelo Tosatti wrote: > >On Tue, May 31, 2011 at 09:05:35PM +0300, Avi Kivity wrote: > >> >> if (is_long_mode(vcpu)) { > >> >> if (!(cr4& X86_CR4_PAE)) > >> >> return 1; > >> > > >> >A new field in vcpu->arch.mmu.base_role for smep is required > >> >for shadow MMU (similar to nxe). > >> > >> I plan to add that with my cr0.wp=0 fixup (it's only needed there, right?) > > > >Sptes instantiated when cr4.smep = 0 should not be used when cr4.smep = > >1, so no (unlikely that guest kernel executes user=1 code anyway, but > >for consistency with other base_role flags). > > Why not? The sptes are interpreted exactly the same. > > sptes are interpreted differently when efer.nxe=1 - if bit 63 is > set, it will fault when nxe=0 and will not fault when nxe=1 (for > non-fetch accesses). So we can't share those sptes. A) CR4.SMEP = 0, spte instantiated via fetch fault of user pte. B) CR4.SMEP = 1, base_role unchanged. C) spte instantiated in A) used, but access should fault instead. Or if you have multiple CPUs with different settings. > >OK then, you'll fix that. > > > > Sure. I'll post the patches as soon as this hits 'next'. > > -- > I have a truly marvellous patch that fixes the bug which this > signature is too narrow to contain. > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html