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=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 7FDEFC43613 for ; Fri, 21 Jun 2019 13:08:19 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 0FB1B2083B for ; Fri, 21 Jun 2019 13:08:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0FB1B2083B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 7D8CA4A332; Fri, 21 Jun 2019 09:08:18 -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 35prOjH32vus; Fri, 21 Jun 2019 09:08:17 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 6B8994A417; Fri, 21 Jun 2019 09:08:17 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id D5CAA4A331 for ; Fri, 21 Jun 2019 09:08:15 -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 yEGJO1Tc7jAU for ; Fri, 21 Jun 2019 09:08:14 -0400 (EDT) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 695164A319 for ; Fri, 21 Jun 2019 09:08:14 -0400 (EDT) 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 Cc: Andre Przywara , Dave Martin 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 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 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm