linux-kernel - Re: [PATCH v2 10/15] KVM: MTRR: introduce var_mtrr

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Date:	Wed, 17 Jun 2015 17:38:34 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
CC:	gleb@...nel.org, mtosatti@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, dmatlack@...gle.com
Subject: Re: [PATCH v2 10/15] KVM: MTRR: introduce var_mtrr_range



On 15/06/2015 10:55, Xiao Guangrong wrote:
> It gets the range for the specified variable MTRR
> 
> Signed-off-by: Xiao Guangrong <guangrong.xiao@...ux.intel.com>
> ---
>  arch/x86/kvm/mtrr.c | 19 +++++++++++++------
>  1 file changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
> index df73149..cb9702d 100644
> --- a/arch/x86/kvm/mtrr.c
> +++ b/arch/x86/kvm/mtrr.c
> @@ -241,10 +241,21 @@ static int fixed_msr_to_range_index(u32 msr)
>  	return fixed_mtrr_seg_unit_range_index(seg, unit);
>  }
>  
> +static void var_mtrr_range(struct kvm_mtrr_range *range, u64 *start, u64 *end)
> +{
> +	u64 mask;
> +
> +	*start = range->base & PAGE_MASK;
> +
> +	mask = range->mask & PAGE_MASK;
> +	mask |= ~0ULL << boot_cpu_data.x86_phys_bits;
> +	*end = ((*start & mask) | ~mask) + 1;

This is just (*start | ~mask) + 1.  I will adjust this.

Paolo

> +}
> +
>  static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
>  {
>  	struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
> -	gfn_t start, end, mask;
> +	gfn_t start, end;
>  	int index;
>  
>  	if (msr == MSR_IA32_CR_PAT || !tdp_enabled ||
> @@ -264,11 +275,7 @@ static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
>  	} else {
>  		/* variable range MTRRs. */
>  		index = (msr - 0x200) / 2;
> -		start = mtrr_state->var_ranges[index].base & PAGE_MASK;
> -		mask = mtrr_state->var_ranges[index].mask & PAGE_MASK;
> -		mask |= ~0ULL << cpuid_maxphyaddr(vcpu);
> -
> -		end = ((start & mask) | ~mask) + 1;
> +		var_mtrr_range(&mtrr_state->var_ranges[index], &start, &end);
>  	}
>  
>  	kvm_zap_gfn_range(vcpu->kvm, gpa_to_gfn(start), gpa_to_gfn(end));
> 
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