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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 9F9B9C43613 for ; Fri, 21 Jun 2019 13:08:22 +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 719DE2083B for ; Fri, 21 Jun 2019 13:08:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="hLtavcpe" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 719DE2083B 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: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=b4X0eDzh0BkMfXr2nq9B1lNXNEGZ5VB5jrZ7jsBwIuo=; b=hLtavcpeuGmjE0 uFgDRb2tTXQvHRbKlORl20+6P40kriIRs5JwOd3R2WmfgxhxrHf9oi7J2f/ar1668+5kT0a9S16jD +X7VWxhBAEkTty1t7qg2ek3d4EoX4gWR3AkrfWqeK7h6E5Hjd9ijCVJNbXwb7B2jxztUCG2051cVB ibdgCMQkDLhQG8SyXW7Icxz80UYOig53KTHMsLFVDrs61mJJWv5k1Byr9fIuSDQ9e1dmuIdG9rAf+ ppATJ7oUG4JENiLw8tThUkQtldEiMeKv81Z+FeI+Zi8r/uHKNYnKlRVlHTI7mKwhoYrGoNyMolu19 U1QXECkS2uetJwx6kMVg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1heJH9-0000VP-K5; Fri, 21 Jun 2019 13:08:19 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1heJH5-0000Ud-UB for linux-arm-kernel@lists.infradead.org; Fri, 21 Jun 2019 13:08:17 +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 F03B2142F; Fri, 21 Jun 2019 06:08:13 -0700 (PDT) Received: from [10.1.197.45] (e112298-lin.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C25193F246; Fri, 21 Jun 2019 06:08:06 -0700 (PDT) Subject: Re: [PATCH 03/59] arm64: Add ARM64_HAS_NESTED_VIRT cpufeature To: Marc Zyngier , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org References: <20190621093843.220980-1-marc.zyngier@arm.com> <20190621093843.220980-4-marc.zyngier@arm.com> From: Julien Thierry Message-ID: <41b1ae35-5b48-7118-3d3e-e227af43010e@arm.com> Date: Fri, 21 Jun 2019 14:08:05 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20190621093843.220980-4-marc.zyngier@arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190621_060816_022334_434EF35E X-CRM114-Status: GOOD ( 18.62 ) 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: Suzuki K Poulose , Andre Przywara , Christoffer Dall , Dave Martin , James Morse , Jintack Lim 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 21/06/2019 10:37, Marc Zyngier wrote: > From: Jintack Lim > > Add a new ARM64_HAS_NESTED_VIRT feature to indicate that the > CPU has the ARMv8.3 nested virtualization capability. > > This will be used to support nested virtualization in KVM. > > Signed-off-by: Jintack Lim > Signed-off-by: Andre Przywara > Signed-off-by: Christoffer Dall > Signed-off-by: Marc Zyngier > --- > .../admin-guide/kernel-parameters.txt | 4 +++ > arch/arm64/include/asm/cpucaps.h | 3 ++- > arch/arm64/include/asm/sysreg.h | 1 + > arch/arm64/kernel/cpufeature.c | 26 +++++++++++++++++++ > 4 files changed, 33 insertions(+), 1 deletion(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 138f6664b2e2..202bb2115d83 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -2046,6 +2046,10 @@ > [KVM,ARM] Allow use of GICv4 for direct injection of > LPIs. > > + kvm-arm.nested= > + [KVM,ARM] Allow nested virtualization in KVM/ARM. > + Default is 0 (disabled) > + Once the kernel has been built with nested guest support, what do we gain from having it disabled by default? It seems a bit odd since the guests have to opt-in for the capability of running guests of their own. Is it it likely to have negative impact a negative impact on the host kernel? Or on guests that do not request use of nested virt? If not I feel that this kernel parameter should be dropped. Cheers, -- Julien Thierry _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel