linux-kernel - Re: [PATCH] KVM: x86: Open code shared_msr

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Date:   Sat, 23 Nov 2019 11:29:49 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: Open code shared_msr_update() in its only
 caller

On 22/11/19 21:04, Sean Christopherson wrote:
> Fold shared_msr_update() into its sole user to eliminate its pointless
> bounds check, its godawful printk, its misleading comment (it's called
> under a global lock), and its woefully inaccurate name.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/kvm/x86.c | 29 +++++++++--------------------
>  1 file changed, 9 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index a256e09f321a..35b571c769bd 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -262,23 +262,6 @@ static void kvm_on_user_return(struct user_return_notifier *urn)
>  	}
>  }
>  
> -static void shared_msr_update(unsigned slot, u32 msr)
> -{
> -	u64 value;
> -	unsigned int cpu = smp_processor_id();
> -	struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
> -
> -	/* only read, and nobody should modify it at this time,
> -	 * so don't need lock */
> -	if (slot >= shared_msrs_global.nr) {
> -		printk(KERN_ERR "kvm: invalid MSR slot!");
> -		return;
> -	}
> -	rdmsrl_safe(msr, &value);
> -	smsr->values[slot].host = value;
> -	smsr->values[slot].curr = value;
> -}
> -
>  void kvm_define_shared_msr(unsigned slot, u32 msr)
>  {
>  	BUG_ON(slot >= KVM_NR_SHARED_MSRS);
> @@ -290,10 +273,16 @@ EXPORT_SYMBOL_GPL(kvm_define_shared_msr);
>  
>  static void kvm_shared_msr_cpu_online(void)
>  {
> -	unsigned i;
> +	unsigned int cpu = smp_processor_id();
> +	struct kvm_shared_msrs *smsr = per_cpu_ptr(shared_msrs, cpu);
> +	u64 value;
> +	int i;
>  
> -	for (i = 0; i < shared_msrs_global.nr; ++i)
> -		shared_msr_update(i, shared_msrs_global.msrs[i]);
> +	for (i = 0; i < shared_msrs_global.nr; ++i) {
> +		rdmsrl_safe(shared_msrs_global.msrs[i], &value);
> +		smsr->values[i].host = value;
> +		smsr->values[i].curr = value;
> +	}
>  }
>  
>  int kvm_set_shared_msr(unsigned slot, u64 value, u64 mask)
> 

Queued, thanks.

Paolo