linux-kernel - Re: [PATCH v2 4/8] KVM: x86: Add helper to get variable MTRR range from MSR index

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Date:   Fri, 12 May 2023 10:21:34 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "guoke@...ontech.com" <guoke@...ontech.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "haiwenyao@...ontech.com" <haiwenyao@...ontech.com>
Subject: Re: [PATCH v2 4/8] KVM: x86: Add helper to get variable MTRR range
 from MSR index

On Thu, 2023-05-11 at 16:33 -0700, Sean Christopherson wrote:
> Add a helper to dedup the logic for retrieving a variable MTRR range
> structure given a variable MTRR MSR index.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Kai Huang <kai.huang@...el.com>

> ---
>  arch/x86/kvm/mtrr.c | 23 +++++++++++++----------
>  1 file changed, 13 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
> index f65ce4b3980f..59851dbebfea 100644
> --- a/arch/x86/kvm/mtrr.c
> +++ b/arch/x86/kvm/mtrr.c
> @@ -31,6 +31,14 @@ static bool is_mtrr_base_msr(unsigned int msr)
>  	return !(msr & 0x1);
>  }
>  
> +static struct kvm_mtrr_range *var_mtrr_msr_to_range(struct kvm_vcpu *vcpu,
> +						    unsigned int msr)
> +{
> +	int index = (msr - 0x200) / 2;
> +
> +	return &vcpu->arch.mtrr_state.var_ranges[index];
> +}
> +
>  static bool msr_mtrr_valid(unsigned msr)
>  {
>  	switch (msr) {
> @@ -314,7 +322,6 @@ static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
>  {
>  	struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
>  	gfn_t start, end;
> -	int index;
>  
>  	if (msr == MSR_IA32_CR_PAT || !tdp_enabled ||
>  	      !kvm_arch_has_noncoherent_dma(vcpu->kvm))
> @@ -332,8 +339,7 @@ static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
>  		end = ~0ULL;
>  	} else {
>  		/* variable range MTRRs. */
> -		index = (msr - 0x200) / 2;
> -		var_mtrr_range(&mtrr_state->var_ranges[index], &start, &end);
> +		var_mtrr_range(var_mtrr_msr_to_range(vcpu, msr), &start, &end);
>  	}
>  
>  	kvm_zap_gfn_range(vcpu->kvm, gpa_to_gfn(start), gpa_to_gfn(end));
> @@ -348,14 +354,12 @@ static void set_var_mtrr_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>  {
>  	struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
>  	struct kvm_mtrr_range *tmp, *cur;
> -	int index;
>  
> -	index = (msr - 0x200) / 2;
> -	cur = &mtrr_state->var_ranges[index];
> +	cur = var_mtrr_msr_to_range(vcpu, msr);
>  
>  	/* remove the entry if it's in the list. */
>  	if (var_mtrr_range_is_valid(cur))
> -		list_del(&mtrr_state->var_ranges[index].node);
> +		list_del(&cur->node);
>  
>  	/*
>  	 * Set all illegal GPA bits in the mask, since those bits must
> @@ -423,11 +427,10 @@ int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
>  	else if (msr == MSR_IA32_CR_PAT)
>  		*pdata = vcpu->arch.pat;
>  	else {	/* Variable MTRRs */
> -		index = (msr - 0x200) / 2;
>  		if (is_mtrr_base_msr(msr))
> -			*pdata = vcpu->arch.mtrr_state.var_ranges[index].base;
> +			*pdata = var_mtrr_msr_to_range(vcpu, msr)->base;
>  		else
> -			*pdata = vcpu->arch.mtrr_state.var_ranges[index].mask;
> +			*pdata = var_mtrr_msr_to_range(vcpu, msr)->mask;
>  
>  		*pdata &= ~kvm_vcpu_reserved_gpa_bits_raw(vcpu);
>  	}
> -- 
> 2.40.1.606.ga4b1b128d6-goog
>