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=-11.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 20B0DC433FE for ; Thu, 3 Dec 2020 16:51:20 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A1481207A5 for ; Thu, 3 Dec 2020 16:51:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A1481207A5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=NtNC/yyFsNyG3yVGzwdQdPdLu3F6dgL4x1TT6NMDRjE=; b=y6ehjNgNcT56C7nzq4/vWzRCX KvxMiWs7TH51PdIo5Z1gMztcgpfbaiQqn39B6sVjAEPpxX1w84QtAfzw/tBfD8q2f45zGKak+/+Ef A3IOVaVGeIumlNfH7P595fKcFN4mmE2nMIxNVgd0ow5ji3PH/FMQeoG/Knx260Ykiz5Z1lPvXJS/q UPWDAj9Qo914+xVsMWbSeEamHU+aa8JM4txQOyq+nRcxLyalO+g7f32f3MzOkOk03GM8M1jN5BIZt YqaustctHspBtHn/Ok8/fmh+E8WnmUOrHArfVkd839LlqAgl8VjTJS9qfnSo6dVA7T0/0OvlRIH48 5MFXWoJnQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kkrnw-0001Vj-Cl; Thu, 03 Dec 2020 16:50:04 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kkrnu-0001V6-0Z for linux-arm-kernel@lists.infradead.org; Thu, 03 Dec 2020 16:50:02 +0000 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 2856011D4; Thu, 3 Dec 2020 08:49:57 -0800 (PST) Received: from [192.168.1.179] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 963473F575; Thu, 3 Dec 2020 08:49:54 -0800 (PST) Subject: Re: [PATCH v6 0/2] MTE support for KVM guest To: Mark Rutland References: <20201127152113.13099-1-steven.price@arm.com> <20201203160943.GG96754@C02TD0UTHF1T.local> From: Steven Price Message-ID: <77e65f06-563b-3b30-ab36-9670e8cc03a4@arm.com> Date: Thu, 3 Dec 2020 16:49:49 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201203160943.GG96754@C02TD0UTHF1T.local> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201203_115002_150919_23EF2237 X-CRM114-Status: GOOD ( 22.89 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , "Dr. David Alan Gilbert" , Andrew Jones , Haibo Xu , Suzuki K Poulose , qemu-devel@nongnu.org, Catalin Marinas , Juan Quintela , Richard Henderson , linux-kernel@vger.kernel.org, Dave Martin , James Morse , linux-arm-kernel@lists.infradead.org, Marc Zyngier , Thomas Gleixner , Will Deacon , kvmarm@lists.cs.columbia.edu, Julien Thierry Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 03/12/2020 16:09, Mark Rutland wrote: > On Fri, Nov 27, 2020 at 03:21:11PM +0000, Steven Price wrote: >> It's been a week, and I think the comments on v5 made it clear that >> enforcing PROT_MTE requirements on the VMM was probably the wrong >> approach. So since I've got swap working correctly without that I >> thought I'd post a v6 which hopefully addresses all the comments so far. >> >> This series adds support for Arm's Memory Tagging Extension (MTE) to >> KVM, allowing KVM guests to make use of it. This builds on the existing >> user space support already in v5.10-rc4, see [1] for an overview. > >> arch/arm64/include/asm/kvm_emulate.h | 3 +++ >> arch/arm64/include/asm/kvm_host.h | 8 ++++++++ >> arch/arm64/include/asm/pgtable.h | 2 +- >> arch/arm64/include/asm/sysreg.h | 3 ++- >> arch/arm64/kernel/mte.c | 18 +++++++++++++----- >> arch/arm64/kvm/arm.c | 9 +++++++++ >> arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 14 ++++++++++++++ >> arch/arm64/kvm/mmu.c | 16 ++++++++++++++++ >> arch/arm64/kvm/sys_regs.c | 20 +++++++++++++++----- >> include/uapi/linux/kvm.h | 1 + >> 10 files changed, 82 insertions(+), 12 deletions(-) > > I note that doesn't fixup arch/arm64/kvm/inject_fault.c, where in > enter_exception64() we have: > > | // TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests) > > ... and IIUC when MTE is present, TCO should be set when delivering an > exception, so I believe that needs to be updated to set TCO. Well spotted! As you say TCO should be set when delivering an exception, so we need the following: - // TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests) + if (kvm_has_mte(vcpu->kvm)) + new |= PSR_TCO_BIT; > Given that MTE-capable HW does that unconditionally, this is going to be > a mess for big.LITTLE. :/ I'm not sure I follow. Either all CPUs support MTE in which this isn't a problem, or the MTE feature just isn't exposed. We don't support a mix of MTE and non-MTE CPUs. There are several aspects of MTE which effective mean it's an all-or-nothing feature for the system. Thanks, Steve _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel