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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 1hidsg-0007oC-Db; Wed, 03 Jul 2019 11:56:58 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hidsd-0007ni-3P for linux-arm-kernel@lists.infradead.org; Wed, 03 Jul 2019 11:56:56 +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 3CC43344; Wed, 3 Jul 2019 04:56:54 -0700 (PDT) Received: from [10.1.197.61] (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 020983F703; Wed, 3 Jul 2019 04:56:52 -0700 (PDT) Subject: Re: [PATCH 04/59] KVM: arm64: nv: Introduce nested virtualization VCPU feature To: Dave Martin References: <20190621093843.220980-1-marc.zyngier@arm.com> <20190621093843.220980-5-marc.zyngier@arm.com> <20190624114329.GO2790@e103592.cambridge.arm.com> From: Marc Zyngier Openpgp: preference=signencrypt Autocrypt: addr=marc.zyngier@arm.com; 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Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190624114329.GO2790@e103592.cambridge.arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190703_045655_239034_60EB5E1C X-CRM114-Status: GOOD ( 13.64 ) 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: kvm@vger.kernel.org, Julien Thierry , Andre Przywara , Suzuki K Poulose , Christoffer Dall , Jintack Lim , James Morse , 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 24/06/2019 12:43, 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 >> --- > > [...] > >> 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); >> +} > > Also, is it worth having a vcpu->arch.flags flag for this, similarly to > SVE and ptrauth? What would we expose through this flag? Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel