From mboxrd@z Thu Jan 1 00:00:00 1970 From: bugzilla-daemon@bugzilla.kernel.org Subject: [Bug 53611] nVMX: Add nested EPT Date: Wed, 27 Feb 2013 08:14:13 +0000 (UTC) Message-ID: <20130227081413.922E611FB5A@bugzilla.kernel.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" To: kvm@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.19.201]:50885 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752752Ab3B0IOQ (ORCPT ); Wed, 27 Feb 2013 03:14:16 -0500 Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id CC5D020341 for ; Wed, 27 Feb 2013 08:14:14 +0000 (UTC) Received: from bugzilla.kernel.org (bugzilla.kernel.org [198.145.19.217]) by mail.kernel.org (Postfix) with ESMTP id 955012025B for ; Wed, 27 Feb 2013 08:14:13 +0000 (UTC) In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: https://bugzilla.kernel.org/show_bug.cgi?id=53611 --- Comment #1 from Nadav Har'El 2013-02-27 08:14:13 --- In addition to the known issues list in the "announce" file attached above, I thought of several more issues that should be considered: 1. When switching back and forth between L1 and L2 it will be a waste to throw away the EPT table already built. So I hope (need to check...) that the EPT table is cached. But what is the cache key - the cr3? But cr3 has a different meaning in L2 and L1, so it might not be correct to use that as the key. 2. When L0 swaps out pages, it needs to remove these entries in all EPT tables, including the cached EPT02 even if not currently used. Does this happen correctly? 3. If L1 uses EPT ("nested EPT") and gives us a malformed EPT12 table, we may need to inject an EPT_MISCONFIGURATION exit when building the merged EPT02 entry. Typically, we do this building (see "fetch" in paging_tmpl.h) when handling an EPT violation exit from L2, so if we encounter this problem instead of reentering L2 immediately, we should exit to L1 with an EPT misconfigration. I'm not sure exactly how to notice this problem. Perhaps the pagetable walking code, which in our case walks EPT12 already notices a problem and does something (#GP perhaps?) and we need to have it do the EPT misconfig instead. But it is possible we need to add additional tests that are not done for normal page tables - in particularly regarding reserved bits, and especially bit 5 (in EPT it is reserved, in normal page tables it is the accessed bit). This issue is low priority, as it only deals with the error path; A well-written L1 will not caused EPT configurations anyway. -- Configure bugmail: https://bugzilla.kernel.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are watching the assignee of the bug.