Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 28 Apr 2021 14:01:56 +0000
From:   Wei Liu <wei.liu@kernel.org>
To:     Vineeth Pillai <viremana@linux.microsoft.com>
Cc:     Lan Tianyu <Tianyu.Lan@microsoft.com>,
        Michael Kelley <mikelley@microsoft.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, Wei Liu <wei.liu@kernel.org>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "K. Y. Srinivasan" <kys@microsoft.com>, x86@kernel.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hyperv@vger.kernel.org
Subject: Re: [PATCH v4 1/7] hyperv: Detect Nested virtualization support for
 SVM
Message-ID: <20210428140156.flf5ie6r2j7os5ch@liuwe-devbox-debian-v2>
References: <cover.1619556430.git.viremana@linux.microsoft.com>
 <8ffa88e6ceb55d283c76b4c5fd9ad0fb1a2cf667.1619556430.git.viremana@linux.microsoft.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <8ffa88e6ceb55d283c76b4c5fd9ad0fb1a2cf667.1619556430.git.viremana@linux.microsoft.com>
Precedence: bulk

On Tue, Apr 27, 2021 at 08:54:50PM +0000, Vineeth Pillai wrote:
> Previously, to detect nested virtualization enlightenment support,
> we were using HV_X64_ENLIGHTENED_VMCS_RECOMMENDED feature bit of
> HYPERV_CPUID_ENLIGHTMENT_INFO.EAX CPUID as docuemented in TLFS:
>  "Bit 14: Recommend a nested hypervisor using the enlightened VMCS
>   interface. Also indicates that additional nested enlightenments
>   may be available (see leaf 0x4000000A)".
> 
> Enlightened VMCS, however, is an Intel only feature so the above
> detection method doesn't work for AMD. So, use the
> HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS.EAX CPUID information ("The
> maximum input value for hypervisor CPUID information.") and this
> works for both AMD and Intel.
> 
> Signed-off-by: Vineeth Pillai <viremana@linux.microsoft.com>

Acked-by: Wei Liu <wei.liu@kernel.org>