From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [PATCH 4/9] Vmi fix highpte Date: Thu, 01 Mar 2007 19:08:25 -0800 Message-ID: <45E79529.9000305@goop.org> References: <200703020254.l222smBB009668@zach-dev.vmware.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200703020254.l222smBB009668@zach-dev.vmware.com> Sender: linux-kernel-owner@vger.kernel.org To: Zachary Amsden Cc: Andi Kleen , Linus Torvalds , Rusty Russell , Chris Wright , Dan Hecht , Dan Arai , Andrew Morton , Virtualization Mailing List , Linux Kernel Mailing List List-Id: virtualization@lists.linuxfoundation.org Zachary Amsden wrote: > Provide a PT map hook for HIGHPTE kernels to designate where they are mapping > page tables. This information is required so the physical address of PTE > updates can be determined; otherwise, the mm layer would have to carry the > physical address all the way to each PTE modification callsite, which is > even more hideous that the macros required to provide the proper hooks. > > So lets not mess up arch neutral code to achieve this, but keep the horror > in an #ifdef HIGHPTE in include/asm-i386/pgtable.h. I had to use macros > here because some types are not yet defined in all the include paths for > this header. > > This patch is absolutely required for HIGHPTE kernels to operate properly > with VMI. > Hm, I don't think this interface will work for Xen. In Xen, whenever a pagetable page gets mapped, it must be mapped RO. map_pt_hook gets called after the mapping has already been created, so its too late for Xen. I was planning on adding kmap_atomic_pte() for use in pte_offset_map*(), which would be wired through to paravirt_ops to allow Xen to make this a RO mapping. Would this be sufficient for you to do your vmi thing? J