From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [kvm-devel] [PATCH] KVM: MMU: Fix guest writes to nonpae pde Date: Sun, 11 Mar 2007 11:32:50 +0100 Message-ID: <20070311103250.GA23396@elte.hu> References: <11736076283998-git-send-email-avi@qumranet.com> <11736076283297-git-send-email-avi@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org To: Avi Kivity Return-path: Content-Disposition: inline In-Reply-To: <11736076283297-git-send-email-avi@qumranet.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org * Avi Kivity wrote: > KVM shadow page tables are always in pae mode, regardless of the guest > setting. This means that a guest pde (mapping 4MB of memory) is > mapped to two shadow pdes (mapping 2MB each). > > When the guest writes to a pte or pde, we intercept the write and > emulate it. We also remove any shadowed mappings corresponding to the > write. Since the mmu did not account for the doubling in the number > of pdes, it removed the wrong entry, resulting in a mismatch between > shadow page tables and guest page tables, followed shortly by guest > memory corruption. > > This patch fixes the problem by detecting the special case of writing > to a non-pae pde and adjusting the address and number of shadow pdes > zapped accordingly. > > Signed-off-by: Avi Kivity tested this with both PAE and non-PAE Linux host and guest - works fine. Acked-by: Ingo Molnar Ingo