linux-kernel - Re: [PATCH v6 8/9] KVM: VMX: Open code VMX preemption timer rate mask in its accessor

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Date: Fri, 15 Mar 2024 23:46:16 +0800
From: Zhao Liu <zhao1.liu@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	Paolo Bonzini <pbonzini@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, Shan Kang <shan.kang@...el.com>,
	Kai Huang <kai.huang@...el.com>, Xin Li <xin3.li@...el.com>
Subject: Re: [PATCH v6 8/9] KVM: VMX: Open code VMX preemption timer rate
 mask in its accessor

On Fri, Mar 08, 2024 at 05:27:24PM -0800, Sean Christopherson wrote:
> Date: Fri,  8 Mar 2024 17:27:24 -0800
> From: Sean Christopherson <seanjc@...gle.com>
> Subject: [PATCH v6 8/9] KVM: VMX: Open code VMX preemption timer rate mask
>  in its accessor
> X-Mailer: git-send-email 2.44.0.278.ge034bb2e1d-goog
> 
> From: Xin Li <xin3.li@...el.com>
> 
> Use vmx_misc_preemption_timer_rate() to get the rate in hardware_setup(),
> and open code the rate's bitmask in vmx_misc_preemption_timer_rate() so
> that the function looks like all the helpers that grab values from
> VMX_BASIC and VMX_MISC MSR values.
> 
> No functional change intended.
> 
> Cc: Shan Kang <shan.kang@...el.com>
> Cc: Kai Huang <kai.huang@...el.com>
> Signed-off-by: Xin Li <xin3.li@...el.com>
> [sean: split to separate patch, write changelog]
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/include/asm/vmx.h | 3 +--
>  arch/x86/kvm/vmx/vmx.c     | 2 +-
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index 6ff179b11235..90ed559076d7 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -148,7 +148,6 @@ static inline u32 vmx_basic_vmcs_mem_type(u64 vmx_basic)
>  	return (vmx_basic & GENMASK_ULL(53, 50)) >> 50;
>  }
>  
> -#define VMX_MISC_PREEMPTION_TIMER_RATE_MASK	GENMASK_ULL(4, 0)
>  #define VMX_MISC_SAVE_EFER_LMA			BIT_ULL(5)
>  #define VMX_MISC_ACTIVITY_HLT			BIT_ULL(6)
>  #define VMX_MISC_ACTIVITY_SHUTDOWN		BIT_ULL(7)
> @@ -162,7 +161,7 @@ static inline u32 vmx_basic_vmcs_mem_type(u64 vmx_basic)
>  
>  static inline int vmx_misc_preemption_timer_rate(u64 vmx_misc)
>  {
> -	return vmx_misc & VMX_MISC_PREEMPTION_TIMER_RATE_MASK;
> +	return vmx_misc & GENMASK_ULL(4, 0);
>  }

I feel keeping VMX_MISC_PREEMPTION_TIMER_RATE_MASK is clearer than
GENMASK_ULL(4, 0), and the former improves code readability.

May not need to drop VMX_MISC_PREEMPTION_TIMER_RATE_MASK?

Thanks,
Zhao