From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6F57C433E0 for ; Wed, 24 Jun 2020 09:38:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BEE0920885 for ; Wed, 24 Jun 2020 09:38:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389825AbgFXJiw (ORCPT ); Wed, 24 Jun 2020 05:38:52 -0400 Received: from foss.arm.com ([217.140.110.172]:53582 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388031AbgFXJiw (ORCPT ); Wed, 24 Jun 2020 05:38:52 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AD8111FB; Wed, 24 Jun 2020 02:38:51 -0700 (PDT) Received: from gaia (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 68A463F73C; Wed, 24 Jun 2020 02:38:50 -0700 (PDT) Date: Wed, 24 Jun 2020 10:38:48 +0100 From: Catalin Marinas To: Peter Maydell Cc: Steven Price , Marc Zyngier , Will Deacon , Dave Martin , lkml - Kernel Mailing List , Thomas Gleixner , kvmarm@lists.cs.columbia.edu, arm-mail-list Subject: Re: [RFC PATCH 0/2] MTE support for KVM guest Message-ID: <20200624093846.GA11863@gaia> References: <20200617123844.29960-1-steven.price@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 23, 2020 at 07:05:07PM +0100, Peter Maydell wrote: > On Wed, 17 Jun 2020 at 13:39, Steven Price wrote: > > These patches add support to KVM to enable MTE within a guest. It is > > based on Catalin's v4 MTE user space series[1]. > > > > [1] http://lkml.kernel.org/r/20200515171612.1020-1-catalin.marinas%40arm.com > > > > Posting as an RFC as I'd like feedback on the approach taken. > > What's your plan for handling tags across VM migration? > Will the kernel expose the tag ram to userspace so we > can copy it from the source machine to the destination > at the same time as we copy the actual ram contents ? Qemu can map the guest memory with PROT_MTE and access the tags directly with LDG/STG instructions. Steven was actually asking in the cover letter whether we should require that the VMM maps the guest memory with PROT_MTE as a guarantee that it can access the guest tags. There is no architecturally visible tag ram (tag storage), that's a microarchitecture detail. -- Catalin