Date:	Thu, 3 Oct 2013 15:11:27 +0300
From:	Gleb Natapov <gleb@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 5/7] KVM: mmu: remove argument to kvm_init_shadow_mmu and
 kvm_init_shadow_ept_mmu

On Thu, Oct 03, 2013 at 01:51:09PM +0200, Paolo Bonzini wrote:
> Il 03/10/2013 13:25, Gleb Natapov ha scritto:
> > On Wed, Oct 02, 2013 at 04:56:14PM +0200, Paolo Bonzini wrote:
> >> The initialization function in mmu.c can always use walk_mmu, which
> >> is known to be vcpu->arch.mmu.  Only init_kvm_nested_mmu is used to
> >> initialize vcpu->arch.nested_mmu.
> >>
> >> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> >> ---
> >>  arch/x86/kvm/mmu.c | 15 +++++++++------
> >>  arch/x86/kvm/mmu.h |  5 ++---
> >>  arch/x86/kvm/svm.c |  4 ++--
> >>  arch/x86/kvm/vmx.c |  4 ++--
> >>  4 files changed, 15 insertions(+), 13 deletions(-)
> >>
> >> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> >> index 40772ef..ac598c8 100644
> >> --- a/arch/x86/kvm/mmu.c
> >> +++ b/arch/x86/kvm/mmu.c
> >> @@ -3742,11 +3742,13 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
> >>  	update_last_pte_bitmap(vcpu, context);
> >>  }
> >>  
> >> -void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *context)
> >> +void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu)
> >>  {
> >>  	bool smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP);
> >> +	struct kvm_mmu *context = vcpu->arch.walk_mmu;
> > I'd rather use &vcpu->arch.mmu here.
> > 
> >> +
> >>  	ASSERT(vcpu);
> >> -	ASSERT(!VALID_PAGE(vcpu->arch.mmu.root_hpa));
> >> +	ASSERT(!VALID_PAGE(context->root_hpa));
> >>  
> >>  	if (!is_paging(vcpu))
> >>  		nonpaging_init_context(vcpu, context);
> >> @@ -3765,11 +3767,12 @@ void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *context)
> >>  }
> >>  EXPORT_SYMBOL_GPL(kvm_init_shadow_mmu);
> >>  
> >> -void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *context,
> >> -		bool execonly)
> >> +void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly)
> >>  {
> >> +	struct kvm_mmu *context = vcpu->arch.walk_mmu;
> >> +
> >>  	ASSERT(vcpu);
> >> -	ASSERT(!VALID_PAGE(vcpu->arch.mmu.root_hpa));
> >> +	ASSERT(!VALID_PAGE(context->root_hpa));
> >>  
> >>  	context->shadow_root_level = kvm_x86_ops->get_tdp_level();
> >>  
> >> @@ -3790,7 +3793,7 @@ EXPORT_SYMBOL_GPL(kvm_init_shadow_ept_mmu);
> >>  
> >>  static void init_kvm_softmmu(struct kvm_vcpu *vcpu)
> >>  {
> >> -	kvm_init_shadow_mmu(vcpu, vcpu->arch.walk_mmu);
> >> +	kvm_init_shadow_mmu(vcpu);
> >>  	vcpu->arch.walk_mmu->set_cr3           = kvm_x86_ops->set_cr3;
> >>  	vcpu->arch.walk_mmu->get_cr3           = get_cr3;
> >>  	vcpu->arch.walk_mmu->get_pdptr         = kvm_pdptr_read;
> > And change walk_mmu to mmu here too for consistency with all other
> > places. Basically if you want to initialize use mmu or nested_mmu.
> > Use walk_mmu pointer only when you need to use mmu.
> 
> Makes sense, especially considering how kvm_init_shadow_mmu initializes 
> vcpu->arch.mmu.base_role directly.
> 
> Something like this (large enough that I'll probably make it a separate 
> patch in v2)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index ac598c8..d1f53cf 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3702,7 +3704,7 @@ static void paging32E_init_context(struct kvm_vcpu *vcpu,
>  
>  static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
>  {
> -	struct kvm_mmu *context = vcpu->arch.walk_mmu;
> +	struct kvm_mmu *context = &vcpu->arch.mmu;
>  
>  	context->base_role.word = 0;
>  	context->page_fault = tdp_page_fault;
> @@ -3745,7 +3747,7 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
>  void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu)
>  {
>  	bool smep = kvm_read_cr4_bits(vcpu, X86_CR4_SMEP);
> -	struct kvm_mmu *context = vcpu->arch.walk_mmu;
> +	struct kvm_mmu *context = &vcpu->arch.mmu;
>  
>  	ASSERT(vcpu);
>  	ASSERT(!VALID_PAGE(context->root_hpa));
> @@ -3759,17 +3761,17 @@ void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu)
>  	else
>  		paging32_init_context(vcpu, context);
>  
> -	vcpu->arch.mmu.base_role.nxe = is_nx(vcpu);
> -	vcpu->arch.mmu.base_role.cr4_pae = !!is_pae(vcpu);
> -	vcpu->arch.mmu.base_role.cr0_wp  = is_write_protection(vcpu);
> -	vcpu->arch.mmu.base_role.smep_andnot_wp
> +	context->base_role.nxe = is_nx(vcpu);
> +	context->base_role.cr4_pae = !!is_pae(vcpu);
> +	context->base_role.cr0_wp  = is_write_protection(vcpu);
> +	context->base_role.smep_andnot_wp
>  		= smep && !is_write_protection(vcpu);
>  }
>  EXPORT_SYMBOL_GPL(kvm_init_shadow_mmu);
>  
>  void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly)
>  {
> -	struct kvm_mmu *context = vcpu->arch.walk_mmu;
> +	struct kvm_mmu *context = &vcpu->arch.mmu;
>  
>  	ASSERT(vcpu);
>  	ASSERT(!VALID_PAGE(context->root_hpa));
> @@ -3793,11 +3795,13 @@ EXPORT_SYMBOL_GPL(kvm_init_shadow_ept_mmu);
>  
>  static void init_kvm_softmmu(struct kvm_vcpu *vcpu)
>  {
> +	struct kvm_mmu *context = &vcpu->arch.mmu;
> +
>  	kvm_init_shadow_mmu(vcpu);
> -	vcpu->arch.walk_mmu->set_cr3           = kvm_x86_ops->set_cr3;
> -	vcpu->arch.walk_mmu->get_cr3           = get_cr3;
> -	vcpu->arch.walk_mmu->get_pdptr         = kvm_pdptr_read;
> -	vcpu->arch.walk_mmu->inject_page_fault = kvm_inject_page_fault;
> +	context->set_cr3           = kvm_x86_ops->set_cr3;
> +	context->get_cr3           = get_cr3;
> +	context->get_pdptr         = kvm_pdptr_read;
> +	context->inject_page_fault = kvm_inject_page_fault;
>  }
>  
>  static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
Yes.

> 
> How far should I go?  Should I also remove the context argument from
> nonpaging_init_context and friends, changing it to a local variable?
> (Doesn't seem like a big improvement in clarity).
> 
If it does not no need to do it. Hard to judge for me without trying.

--
			Gleb.
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