From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH][RFC] pte notifiers -- support for external page tables References: <11890207643068-git-send-email-avi@qumranet.com> From: Andi Kleen In-Reply-To: <11890207643068-git-send-email-avi@qumranet.com> Date: 06 Sep 2007 15:28:58 +0200 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Avi Kivity , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: Avi Kivity writes: > > pte notifiers are different from paravirt_ops: they extend the normal > page tables rather than replace them; and they provide high-level information > such as the vma and the virtual address for the driver to use. Sounds like a locking horror to me. To do anything with page tables you need locks. Both for the kernel page tables and for your new tables. What happens when people add all things of complicated operations in these notifiers? That will likely happen and then everytime you change something in VM code they will break. This has the potential to increase the cost of maintaining VM code considerably, which would be a bad thing. This is quite different from paravirt ops because low level pvops can typically run lockless by just doing some kind of hypercall directly. But that won't work for maintaining your custom page tables. -Andi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org