linux-kernel - Re: [PATCH] kvm: x86: refine kvm_get_arch

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Date:   Tue, 4 Jun 2019 18:09:16 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Xiaoyao Li <xiaoyao.li@...ux.intel.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kvm: x86: refine kvm_get_arch_capabilities()

On 19/04/19 04:16, Xiaoyao Li wrote:
> 1. Using X86_FEATURE_ARCH_CAPABILITIES to enumerate the existence of
> MSR_IA32_ARCH_CAPABILITIES to avoid using rdmsrl_safe().
> 
> 2. Since kvm_get_arch_capabilities() is only used in this file, making
> it static.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@...ux.intel.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 1 -
>  arch/x86/kvm/x86.c              | 8 ++++----
>  2 files changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index a9d03af34030..d4ae67870764 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1526,7 +1526,6 @@ int kvm_pv_send_ipi(struct kvm *kvm, unsigned long ipi_bitmap_low,
>  		    unsigned long ipi_bitmap_high, u32 min,
>  		    unsigned long icr, int op_64_bit);
>  
> -u64 kvm_get_arch_capabilities(void);
>  void kvm_define_shared_msr(unsigned index, u32 msr);
>  int kvm_set_shared_msr(unsigned index, u64 val, u64 mask);
>  
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index a0d1fc80ac5a..ba8e269a8cd2 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1205,11 +1205,12 @@ static u32 msr_based_features[] = {
>  
>  static unsigned int num_msr_based_features;
>  
> -u64 kvm_get_arch_capabilities(void)
> +static u64 kvm_get_arch_capabilities(void)
>  {
> -	u64 data;
> +	u64 data = 0;
>  
> -	rdmsrl_safe(MSR_IA32_ARCH_CAPABILITIES, &data);
> +	if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
> +		rdmsrl(MSR_IA32_ARCH_CAPABILITIES, data);
>  
>  	/*
>  	 * If we're doing cache flushes (either "always" or "cond")
> @@ -1225,7 +1226,6 @@ u64 kvm_get_arch_capabilities(void)
>  
>  	return data;
>  }
> -EXPORT_SYMBOL_GPL(kvm_get_arch_capabilities);
>  
>  static int kvm_get_msr_feature(struct kvm_msr_entry *msr)
>  {
> 

Queued, thanks.

Paolo