Re: [PATCH v2 11/15] KVM: MTRR: sort variable MTRRs

[Paolo Bonzini]

On 15/06/2015 10:55, Xiao Guangrong wrote:
> Sort all valid variable MTRRs based on its base address, it will help us to
> check a range to see if it's fully contained in variable MTRRs
> 
> Signed-off-by: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
> ---
>  arch/x86/include/asm/kvm_host.h |  3 ++
>  arch/x86/kvm/mtrr.c             | 63 ++++++++++++++++++++++++++++++++++-------
>  arch/x86/kvm/x86.c              |  2 +-
>  arch/x86/kvm/x86.h              |  1 +
>  4 files changed, 58 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index f735548..f2d60cc 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -345,12 +345,15 @@ enum {
>  struct kvm_mtrr_range {
>  	u64 base;
>  	u64 mask;
> +	struct list_head node;
>  };
>  
>  struct kvm_mtrr {
>  	struct kvm_mtrr_range var_ranges[KVM_NR_VAR_MTRR];
>  	mtrr_type fixed_ranges[KVM_NR_FIXED_MTRR_REGION];
>  	u64 deftype;
> +
> +	struct list_head head;
>  };
>  
>  struct kvm_vcpu_arch {
> diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
> index cb9702d..c06ec13 100644
> --- a/arch/x86/kvm/mtrr.c
> +++ b/arch/x86/kvm/mtrr.c
> @@ -281,6 +281,52 @@ static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
>  	kvm_zap_gfn_range(vcpu->kvm, gpa_to_gfn(start), gpa_to_gfn(end));
>  }
>  
> +static bool var_mtrr_range_is_valid(struct kvm_mtrr_range *range)
> +{
> +	u64 start, end;
> +
> +	if (!(range->mask & (1 << 11)))
> +		return false;
> +
> +	var_mtrr_range(range, &start, &end);
> +	return end > start;
> +}

I think this test is incorrect; it is always true unless end overflows
to zero, which cannot happen because writing an invalid value to the
MSR causes a #GP.

Paolo

> +static void set_var_mtrr_start(struct kvm_mtrr *mtrr_state, int index)
> +{
> +	/* remove the entry if it's in the list. */
> +	if (var_mtrr_range_is_valid(&mtrr_state->var_ranges[index]))
> +		list_del(&mtrr_state->var_ranges[index].node);
> +}
> +
> +static void set_var_mtrr_end(struct kvm_mtrr *mtrr_state, int index)
> +{
> +	struct kvm_mtrr_range *tmp, *cur = &mtrr_state->var_ranges[index];
> +
> +	/* add it to the list if it's valid. */
> +	if (var_mtrr_range_is_valid(&mtrr_state->var_ranges[index])) {
> +		list_for_each_entry(tmp, &mtrr_state->head, node)
> +			if (cur->base < tmp->base)
> +				list_add_tail(&cur->node, &tmp->node);
> +
> +		list_add_tail(&cur->node, &mtrr_state->head);
> +	}
> +}
> +
> +static void set_var_mtrr_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> +{
> +	int index, is_mtrr_mask;
> +
> +	index = (msr - 0x200) / 2;
> +	is_mtrr_mask = msr - 0x200 - 2 * index;
> +	set_var_mtrr_start(&vcpu->arch.mtrr_state, index);
> +	if (!is_mtrr_mask)
> +		vcpu->arch.mtrr_state.var_ranges[index].base = data;
> +	else
> +		vcpu->arch.mtrr_state.var_ranges[index].mask = data;
> +	set_var_mtrr_end(&vcpu->arch.mtrr_state, index);
> +}
> +
>  int kvm_mtrr_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>  {
>  	int index;
> @@ -295,16 +341,8 @@ int kvm_mtrr_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>  		vcpu->arch.mtrr_state.deftype = data;
>  	else if (msr == MSR_IA32_CR_PAT)
>  		vcpu->arch.pat = data;
> -	else {	/* Variable MTRRs */
> -		int is_mtrr_mask;
> -
> -		index = (msr - 0x200) / 2;
> -		is_mtrr_mask = msr - 0x200 - 2 * index;
> -		if (!is_mtrr_mask)
> -			vcpu->arch.mtrr_state.var_ranges[index].base = data;
> -		else
> -			vcpu->arch.mtrr_state.var_ranges[index].mask = data;
> -	}
> +	else
> +		set_var_mtrr_msr(vcpu, msr, data);
>  
>  	update_mtrr(vcpu, msr);
>  	return 0;
> @@ -350,6 +388,11 @@ int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
>  	return 0;
>  }
>  
> +void kvm_vcpu_mtrr_init(struct kvm_vcpu *vcpu)
> +{
> +	INIT_LIST_HEAD(&vcpu->arch.mtrr_state.head);
> +}
> +
>  u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn)
>  {
>  	struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 2ffad7f..6574fa3 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7379,13 +7379,13 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
>  {
>  	int r;
>  
> +	kvm_vcpu_mtrr_init(vcpu);
>  	r = vcpu_load(vcpu);
>  	if (r)
>  		return r;
>  	kvm_vcpu_reset(vcpu, false);
>  	kvm_mmu_setup(vcpu);
>  	vcpu_put(vcpu);
> -
>  	return r;
>  }
>  
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index aeb0bb2..0e4727c 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -162,6 +162,7 @@ int kvm_write_guest_virt_system(struct x86_emulate_ctxt *ctxt,
>  	gva_t addr, void *val, unsigned int bytes,
>  	struct x86_exception *exception);
>  
> +void kvm_vcpu_mtrr_init(struct kvm_vcpu *vcpu);
>  u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn);
>  bool kvm_mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data);
>  int kvm_mtrr_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data);
> 
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