RE: [PATCH 1/7] hyperv: Detect Nested virtualization support for SVM

From: Michael Kelley <mikelley@microsoft.com>
To: Vineeth Pillai <viremana@linux.microsoft.com>,
	Tianyu Lan <Tianyu.Lan@microsoft.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	vkuznets <vkuznets@redhat.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>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	KY Srinivasan <kys@microsoft.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>
Subject: RE: [PATCH 1/7] hyperv: Detect Nested virtualization support for SVM
Date: Wed, 7 Apr 2021 19:55:15 +0000	[thread overview]
Message-ID: <MWHPR21MB159327E855DAC5BEE4B8A38DD7759@MWHPR21MB1593.namprd21.prod.outlook.com> (raw)
In-Reply-To: <e14dac75ff1088b2c4bea361954b37e414edd03c.1617804573.git.viremana@linux.microsoft.com>

From: Vineeth Pillai <viremana@linux.microsoft.com> Sent: Wednesday, April 7, 2021 7:41 AM
> 
> Detect nested features exposed by Hyper-V if SVM is enabled.
> 
> Signed-off-by: Vineeth Pillai <viremana@linux.microsoft.com>
> ---
>  arch/x86/kernel/cpu/mshyperv.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 3546d3e21787..4d364acfe95d 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -325,9 +325,17 @@ static void __init ms_hyperv_init_platform(void)
>  			ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
>  	}
> 
> -	if (ms_hyperv.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED) {
> +	/*
> +	 * AMD does not need enlightened VMCS as VMCB is already a
> +	 * datastructure in memory. We need to get the nested
> +	 * features if SVM is enabled.
> +	 */
> +	if (boot_cpu_has(X86_FEATURE_SVM) ||
> +	    ms_hyperv.hints & HV_X64_ENLIGHTENED_VMCS_RECOMMENDED) {
>  		ms_hyperv.nested_features =
>  			cpuid_eax(HYPERV_CPUID_NESTED_FEATURES);
> +		pr_info("Hyper-V nested_features: 0x%x\n",

Nit:  Most other similar lines put the colon in a different place:

		pr_info("Hyper-V: nested features 0x%x\n",

One of these days, I'm going to fix the ones that don't follow this
pattern. :-)

> +			ms_hyperv.nested_features);
>  	}
> 
>  	/*
> --
> 2.25.1