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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 88A5FC0650E for ; Wed, 3 Jul 2019 16:27:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 68F95218BA for ; Wed, 3 Jul 2019 16:27:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727117AbfGCQ1L (ORCPT ); Wed, 3 Jul 2019 12:27:11 -0400 Received: from foss.arm.com ([217.140.110.172]:52062 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726881AbfGCQ1K (ORCPT ); Wed, 3 Jul 2019 12:27:10 -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 DF292344; Wed, 3 Jul 2019 09:27:09 -0700 (PDT) Received: from e103592.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1E05F3F718; Wed, 3 Jul 2019 09:27:09 -0700 (PDT) Date: Wed, 3 Jul 2019 17:27:07 +0100 From: Dave Martin To: Marc Zyngier Cc: kvm@vger.kernel.org, Andre Przywara , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 04/59] KVM: arm64: nv: Introduce nested virtualization VCPU feature Message-ID: <20190703162706.GV2790@e103592.cambridge.arm.com> References: <20190621093843.220980-1-marc.zyngier@arm.com> <20190621093843.220980-5-marc.zyngier@arm.com> <20190624112851.GM2790@e103592.cambridge.arm.com> <01e61a51-5bf0-8943-6f68-7a5cea59f093@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <01e61a51-5bf0-8943-6f68-7a5cea59f093@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Jul 03, 2019 at 12:53:58PM +0100, Marc Zyngier wrote: > On 24/06/2019 12:28, Dave Martin wrote: > > On Fri, Jun 21, 2019 at 10:37:48AM +0100, 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); > >> +} > >> + > >> +#endif /* __ARM64_KVM_NESTED_H */ > >> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h > >> index d819a3e8b552..563e2a8bae93 100644 > >> --- a/arch/arm64/include/uapi/asm/kvm.h > >> +++ b/arch/arm64/include/uapi/asm/kvm.h > >> @@ -106,6 +106,7 @@ struct kvm_regs { > >> #define KVM_ARM_VCPU_SVE 4 /* enable SVE for this CPU */ > >> #define KVM_ARM_VCPU_PTRAUTH_ADDRESS 5 /* VCPU uses address authentication */ > >> #define KVM_ARM_VCPU_PTRAUTH_GENERIC 6 /* VCPU uses generic authentication */ > >> +#define KVM_ARM_VCPU_NESTED_VIRT 7 /* Support nested virtualization */ > > > > This seems weirdly named: > > > > Isn't the feature we're exposing here really EL2? In that case, the > > feature the guest gets with this flag enabled is plain virtualisation, > > possibly with the option to nest further. > > > > Does the guest also get nested virt (i.e., recursively nested virt from > > the host's PoV) as a side effect, or would require an explicit extra > > flag? > > So far, there is no extra flag to describe further nesting, and it > directly comes from EL2 being emulated. I don't mind renaming this to > KVM_ARM_VCPU_HAS_EL2, or something similar... Whether we want userspace > to control the exposure of the nesting capability (i.e. EL2 with > ARMv8.3-NV) is another question. Agreed. KVM_ARM_VCPU_HAS_EL2 seems a reasonable name to me. If we have have an internal flag in vcpu_arch.flags we could call that something different (i.e., keep the NESTED_VIRT naming) if it's natural to do so. Cheers ---Dave