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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham 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 B88C0C43381 for ; Fri, 1 Mar 2019 14:45:02 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 8423E20851 for ; Fri, 1 Mar 2019 14:45:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="nru6OfXF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8423E20851 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-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=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=xSSYaeeiz/39lGhi5QDIM4ObYp56sR4iN3631mg1Gfo=; b=nru6OfXF57qHqn zVpOBE7Hjkmyg2pRE/fefWTbp04zAz6SY9D+2XM8fZQPdPlSiC9Mmr8MUeDwgnFqj7XC3I9wZHaHK PZw5yZndKY2sTmjzNP+GuM1Bu03ZNVu9zzItEDdsRYXhfCy7nMEDxeEdJfwjsUAaT6CGOzgWXUbOo jBx8zMQmXuletKqJndPW8owx0ywguFN8hEkw8YxyLxhv3QiJefstws3MZTSvPJkDvMyDlwY+Brkv8 k8cmsr3Q6Vg0yUiMMOQH6GsM1ohszabcBG6dhV3MR1P+7R+l61OkKiiptknnz8pcTT3SGYOI6k2qr 4j0ZFSYVNkVjn1b5Y0cQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gzjPJ-000813-1B; Fri, 01 Mar 2019 14:45:01 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gzjPF-00080X-8q for linux-arm-kernel@lists.infradead.org; Fri, 01 Mar 2019 14:44:58 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B2602A78; Fri, 1 Mar 2019 06:44:56 -0800 (PST) Received: from e103592.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E383F3F720; Fri, 1 Mar 2019 06:44:54 -0800 (PST) Date: Fri, 1 Mar 2019 14:44:52 +0000 From: Dave Martin To: Julien Thierry Subject: Re: [PATCH v5 06/26] arm64/sve: Check SVE virtualisability Message-ID: <20190301144452.GG3567@e103592.cambridge.arm.com> References: <1550519559-15915-1-git-send-email-Dave.Martin@arm.com> <1550519559-15915-7-git-send-email-Dave.Martin@arm.com> <64764e35-c243-e642-a868-5b9e221813c7@arm.com> <20190226120630.GH3567@e103592.cambridge.arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190301_064457_318415_6E0ABAF8 X-CRM114-Status: GOOD ( 24.89 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Okamoto Takayuki , Christoffer Dall , Ard Biesheuvel , Marc Zyngier , Catalin Marinas , Will Deacon , Zhang Lei , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Mar 01, 2019 at 12:39:52PM +0000, Julien Thierry wrote: > > > On 26/02/2019 12:06, Dave Martin wrote: > > On Wed, Feb 20, 2019 at 11:12:49AM +0000, Julien Thierry wrote: > >> Hi Dave, > >> > >> On 18/02/2019 19:52, Dave Martin wrote: [...] > >>> + /* > >>> + * Mismatches above sve_max_virtualisable_vl are fine, since > >>> + * no guest is allowed to configure ZCR_EL2.LEN to exceed this: > >>> + */ > >>> + if (sve_vl_from_vq(bit_to_vq(b)) <= sve_max_virtualisable_vl) { > >>> + pr_warn("SVE: cpu%d: Unsupported vector length(s) present\n", > >> > >> Nit: might be good to specify that the vector length is unsupported for > >> virtualisation. > >> > >> Also, since KVM is the one deciding what to do with the information, > >> should we have a warning here? But I can understand that knowing which > >> CPUs are introducing unsupported vector length, maybe using pr_devel() > >> instead of pr_warn() > > > > These warnings are really for consumption by SoC vendors, not users: > > my aim is to flag up systems that we consider broken (or at least, > > unsuitable for running KVM). > > > > So I prefer to make this noisy and limit the amount of "useful" > > information people might be tempted to programmatically scrape from > > dmesg. > > > > cpufeatures uses pr_warn("SANITY CHECK: [...]") here. Maybe I should > > stick "SANITY CHECK" in here too? I will also try to make the commit > > message more explicit and/or add comments to make the intent of the code > > clearer. > > > > It may also make sense to make this noise even if KVM isn't enabled > > (which is a rare case anyhow). > > > > Thoughts? > > As I explained later in the patch series, I missed the fact that this > function was for late secondary CPUs. I think things are fine like this > (just add the bit about the vector lenght not being supported for > virtualisation). I've now reworked all this a bit: I probe for the largest vector length than be offered to guests, and if this is less than the host's maximum vector length then I print a one-off warning saying what limit KVM is clamping guests' vector length to. Elsewhere, I now just use the probed value as the maximum vector length, rather than duplicating the bounds checking logic. This approach seems simpler, and is hoepfully a bit more self- explanatory -- so please take a look when I repost :) Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel