linux-kernel - Re: [PATCH MANUALSEL 5.4 1/2] KVM: nVMX: eVMCS: Filter out VM_EXIT_SAVE_VMX_PREEMPTION

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Message-ID: <d1d25157-6511-a37d-0e19-2ef8335a7882@redhat.com>
Date:   Thu, 10 Feb 2022 17:35:56 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, kvm@...r.kernel.org
Subject: Re: [PATCH MANUALSEL 5.4 1/2] KVM: nVMX: eVMCS: Filter out
 VM_EXIT_SAVE_VMX_PREEMPTION_TIMER

On 2/9/22 19:57, Sasha Levin wrote:
> From: Vitaly Kuznetsov <vkuznets@...hat.com>
> 
> [ Upstream commit 7a601e2cf61558dfd534a9ecaad09f5853ad8204 ]

Acked-by: Paolo Bonzini <pbonzini@...hat.com>

Paolo

> Enlightened VMCS v1 doesn't have VMX_PREEMPTION_TIMER_VALUE field,
> PIN_BASED_VMX_PREEMPTION_TIMER is also filtered out already so it makes
> sense to filter out VM_EXIT_SAVE_VMX_PREEMPTION_TIMER too.
> 
> Note, none of the currently existing Windows/Hyper-V versions are known
> to enable 'save VMX-preemption timer value' when eVMCS is in use, the
> change is aimed at making the filtering future proof.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> Message-Id: <20220112170134.1904308-3-vkuznets@...hat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>   arch/x86/kvm/vmx/evmcs.h | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/vmx/evmcs.h b/arch/x86/kvm/vmx/evmcs.h
> index 07ebf6882a458..632bed227152e 100644
> --- a/arch/x86/kvm/vmx/evmcs.h
> +++ b/arch/x86/kvm/vmx/evmcs.h
> @@ -58,7 +58,9 @@ DECLARE_STATIC_KEY_FALSE(enable_evmcs);
>   	 SECONDARY_EXEC_SHADOW_VMCS |					\
>   	 SECONDARY_EXEC_TSC_SCALING |					\
>   	 SECONDARY_EXEC_PAUSE_LOOP_EXITING)
> -#define EVMCS1_UNSUPPORTED_VMEXIT_CTRL (VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL)
> +#define EVMCS1_UNSUPPORTED_VMEXIT_CTRL					\
> +	(VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL |				\
> +	 VM_EXIT_SAVE_VMX_PREEMPTION_TIMER)
>   #define EVMCS1_UNSUPPORTED_VMENTRY_CTRL (VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL)
>   #define EVMCS1_UNSUPPORTED_VMFUNC (VMX_VMFUNC_EPTP_SWITCHING)
>