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 04492C43613 for ; Fri, 21 Jun 2019 13:08:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D7C4D2083B for ; Fri, 21 Jun 2019 13:08:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726822AbfFUNI3 (ORCPT ); Fri, 21 Jun 2019 09:08:29 -0400 Received: from foss.arm.com ([217.140.110.172]:60184 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726285AbfFUNI2 (ORCPT ); Fri, 21 Jun 2019 09:08:28 -0400 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 7B006142F; Fri, 21 Jun 2019 06:08:28 -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 407DF3F246; Fri, 21 Jun 2019 06:08:27 -0700 (PDT) Subject: Re: [PATCH 04/59] KVM: arm64: nv: Introduce nested virtualization VCPU feature To: Marc Zyngier , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org Cc: Andre Przywara , Christoffer Dall , Dave Martin , Jintack Lim , James Morse , Suzuki K Poulose References: <20190621093843.220980-1-marc.zyngier@arm.com> <20190621093843.220980-5-marc.zyngier@arm.com> From: Julien Thierry Message-ID: <95a96d6c-ada4-289c-2634-9877fa04086a@arm.com> Date: Fri, 21 Jun 2019 14:08:26 +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: <20190621093843.220980-5-marc.zyngier@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 21/06/2019 10:37, Marc Zyngier wrote: > From: Christoffer Dall > > Introduce the feature bit and a primitive that checks if the feature is > set behind a static key check based on the cpus_have_const_cap check. > > Checking nested_virt_in_use() on systems without nested virt enabled > should have neglgible overhead. > > We don't yet allow userspace to actually set this feature. > > Signed-off-by: Christoffer Dall > Signed-off-by: Marc Zyngier > --- > arch/arm/include/asm/kvm_nested.h | 9 +++++++++ > arch/arm64/include/asm/kvm_nested.h | 13 +++++++++++++ > arch/arm64/include/uapi/asm/kvm.h | 1 + > 3 files changed, 23 insertions(+) > create mode 100644 arch/arm/include/asm/kvm_nested.h > create mode 100644 arch/arm64/include/asm/kvm_nested.h > > diff --git a/arch/arm/include/asm/kvm_nested.h b/arch/arm/include/asm/kvm_nested.h > new file mode 100644 > index 000000000000..124ff6445f8f > --- /dev/null > +++ b/arch/arm/include/asm/kvm_nested.h > @@ -0,0 +1,9 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __ARM_KVM_NESTED_H > +#define __ARM_KVM_NESTED_H > + > +#include > + > +static inline bool nested_virt_in_use(const struct kvm_vcpu *vcpu) { return false; } > + > +#endif /* __ARM_KVM_NESTED_H */ > diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h > new file mode 100644 > index 000000000000..8a3d121a0b42 > --- /dev/null > +++ b/arch/arm64/include/asm/kvm_nested.h > @@ -0,0 +1,13 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __ARM64_KVM_NESTED_H > +#define __ARM64_KVM_NESTED_H > + > +#include > + > +static inline bool nested_virt_in_use(const struct kvm_vcpu *vcpu) > +{ > + return cpus_have_const_cap(ARM64_HAS_NESTED_VIRT) && > + test_bit(KVM_ARM_VCPU_NESTED_VIRT, vcpu->arch.features); Nit: You could make it even cheaper for some systems by adding IS_DEFINED(CONFIG_ARM64_VHE). It would also make the dependency between NV and VHE more explicit. Otherwise: Reviewed-by: Julien Thierry Cheers, -- Julien Thierry