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 Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by smtp.lore.kernel.org (Postfix) with ESMTP id 51EC4C433EF for ; Wed, 8 Jun 2022 18:41:50 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id C6AC14B20A; Wed, 8 Jun 2022 14:41:49 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id W2dllxUxl1Jq; Wed, 8 Jun 2022 14:41:48 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 66CC74B271; Wed, 8 Jun 2022 14:41:48 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 44B6A4B20A for ; Wed, 8 Jun 2022 14:41:47 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id OtL2TMb79Yn6 for ; Wed, 8 Jun 2022 14:41:46 -0400 (EDT) Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 130194A3A5 for ; Wed, 8 Jun 2022 14:41:45 -0400 (EDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 60D6261C1D; Wed, 8 Jun 2022 18:41:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C728C34116; Wed, 8 Jun 2022 18:41:41 +0000 (UTC) Date: Wed, 8 Jun 2022 19:41:37 +0100 From: Catalin Marinas To: Peter Collingbourne Subject: Re: [PATCH 59/89] KVM: arm64: Do not support MTE for protected VMs Message-ID: References: <20220519134204.5379-1-will@kernel.org> <20220519134204.5379-60-will@kernel.org> <87v8tgltqy.wl-maz@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Cc: kernel-team@android.com, kvm@vger.kernel.org, Marc Zyngier , Linux ARM , Michael Roth , Chao Peng , Andy Lutomirski , Will Deacon , kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Mon, Jun 06, 2022 at 05:20:39PM -0700, Peter Collingbourne wrote: > On Sat, Jun 4, 2022 at 1:26 AM Marc Zyngier wrote: > > But the bigger picture here is what ensures that the host cannot mess > > with the guest tags? I don't think we have a any mechanism to > > guarantee that, specially on systems where the tags are only a memory > > carve-out, which the host could map and change at will. > > Right, I forgot about that. We probably only want to expose MTE to > guests if we have some indication (through the device tree or ACPI) of > how to protect the guest tag storage. I think this would be useful irrespective of MTE. Some SoCs (though I hope very rare these days) may allow for physical aliasing of RAM but if the host stage 2 only protects one of the aliases, it's not of much use. I am yet to fully understand how pKVM works but with the separation of the hyp from the host kernel, it may have to actually parse the DT/ACPI/EFI tables itself if it cannot rely on what the host kernel told it. IIUC currently it creates an idmap at stage 2 for the host kernel, only unmapped if the memory was assigned to a guest. But not sure what happens with the rest of the host physical address space (devices etc.), I presume they are fully accessible by the host kernel in stage 2. -- Catalin _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm