Re: [PATCH] KVM: x86: VMX: hyper-v: Enlightened MSR-Bitmap support

From: Paolo Bonzini <pbonzini@redhat.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>, kvm@vger.kernel.org
Cc: x86@kernel.org, "Radim Krčmář" <rkrcmar@redhat.com>,
	"Roman Kagan" <rkagan@virtuozzo.com>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	"Haiyang Zhang" <haiyangz@microsoft.com>,
	"Stephen Hemminger" <sthemmin@microsoft.com>,
	"Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>,
	"Mohammed Gamal" <mmorsy@redhat.com>,
	"Cathy Avery" <cavery@redhat.com>,
	"Tianyu Lan" <Tianyu.Lan@microsoft.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: x86: VMX: hyper-v: Enlightened MSR-Bitmap support
Date: Fri, 13 Apr 2018 15:52:30 +0200	[thread overview]
Message-ID: <ef082ed6-1af9-a578-d9da-e0874cc4769c@redhat.com> (raw)
In-Reply-To: <20180412152508.27617-1-vkuznets@redhat.com>

On 12/04/2018 17:25, Vitaly Kuznetsov wrote:
> @@ -5335,6 +5353,9 @@ static void __always_inline vmx_disable_intercept_for_msr(unsigned long *msr_bit
>  	if (!cpu_has_vmx_msr_bitmap())
>  		return;
>  
> +	if (static_branch_unlikely(&enable_emsr_bitmap))
> +		evmcs_touch_msr_bitmap();
> +
>  	/*
>  	 * See Intel PRM Vol. 3, 20.6.9 (MSR-Bitmap Address). Early manuals
>  	 * have the write-low and read-high bitmap offsets the wrong way round.
> @@ -5370,6 +5391,9 @@ static void __always_inline vmx_enable_intercept_for_msr(unsigned long *msr_bitm
>  	if (!cpu_has_vmx_msr_bitmap())
>  		return;
>  
> +	if (static_branch_unlikely(&enable_emsr_bitmap))
> +		evmcs_touch_msr_bitmap();

I'm not sure about the "unlikely".  Can you just check current_evmcs
instead (dropping the static key completely)?

The function, also, is small enough that inlining should be beneficial.

Paolo