linux-kernel - Re: [Patch v4 14/18] KVM: mmu: Initialize kvm_mmu_memory_cache.gfp_zero to __GFP

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Message-ID: <ZBzSgI2mkpl3QTNt@google.com>
Date:   Thu, 23 Mar 2023 15:28:16 -0700
From:   David Matlack <dmatlack@...gle.com>
To:     Vipin Sharma <vipinsh@...gle.com>
Cc:     seanjc@...gle.com, pbonzini@...hat.com, bgardon@...gle.com,
        jmattson@...gle.com, mizhang@...gle.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [Patch v4 14/18] KVM: mmu: Initialize
 kvm_mmu_memory_cache.gfp_zero to __GFP_ZERO by default

On Mon, Mar 06, 2023 at 02:41:23PM -0800, Vipin Sharma wrote:
> Set __GFP_ZERO to gfp_zero in default initizliation of struct
> kvm_mmu_memory_cache{}
> 
> All of the users of default initialization code of struct
> kvm_mmu_memory_cache{} explicitly sets gfp_zero to __GFP_ZERO. This can
> be moved to common initialization logic.

If that were true we could get rid of gfp_zero entirely and hard-code
__GFP_ZERO in the memory allocator! mmu_shadowed_info_cache is the one
that does not set __GFP_ZERO.

> 
> Signed-off-by: Vipin Sharma <vipinsh@...gle.com>
> ---
>  arch/arm64/kvm/arm.c      | 1 -
>  arch/arm64/kvm/mmu.c      | 1 -
>  arch/riscv/kvm/mmu.c      | 1 -
>  arch/riscv/kvm/vcpu.c     | 1 -
>  arch/x86/kvm/mmu/mmu.c    | 6 ------
>  include/linux/kvm_types.h | 4 +++-
>  6 files changed, 3 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 2b3d88e4ace8..b4243978d962 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -331,7 +331,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>  	bitmap_zero(vcpu->arch.features, KVM_VCPU_MAX_FEATURES);
>  
>  	INIT_KVM_MMU_MEMORY_CACHE(&vcpu->arch.mmu_page_cache);
> -	vcpu->arch.mmu_page_cache.gfp_zero = __GFP_ZERO;
>  
>  	/*
>  	 * Default value for the FP state, will be overloaded at load
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 8a56f071ca66..133eba96c41f 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -904,7 +904,6 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
>  	if (is_protected_kvm_enabled())
>  		return -EPERM;
>  
> -	cache.gfp_zero = __GFP_ZERO;
>  	size += offset_in_page(guest_ipa);
>  	guest_ipa &= PAGE_MASK;
>  
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index bdd8c17958dd..62550fd91c70 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -353,7 +353,6 @@ int kvm_riscv_gstage_ioremap(struct kvm *kvm, gpa_t gpa,
>  	phys_addr_t addr, end;
>  	KVM_MMU_MEMORY_CACHE(pcache);
>  
> -	pcache.gfp_zero = __GFP_ZERO;
>  	if (in_atomic)
>  		pcache.gfp_custom = GFP_ATOMIC | __GFP_ACCOUNT;
>  
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index bc743e9122d1..f5a96ed1e426 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -164,7 +164,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>  	/* Mark this VCPU never ran */
>  	vcpu->arch.ran_atleast_once = false;
>  	INIT_KVM_MMU_MEMORY_CACHE(&vcpu->arch.mmu_page_cache);
> -	vcpu->arch.mmu_page_cache.gfp_zero = __GFP_ZERO;
>  	bitmap_zero(vcpu->arch.isa, RISCV_ISA_EXT_MAX);
>  
>  	/* Setup ISA features available to VCPU */
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index b706087ef74e..d96afc849ee8 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5963,14 +5963,11 @@ int kvm_mmu_create(struct kvm_vcpu *vcpu)
>  
>  	INIT_KVM_MMU_MEMORY_CACHE(&vcpu->arch.mmu_pte_list_desc_cache);
>  	vcpu->arch.mmu_pte_list_desc_cache.kmem_cache = pte_list_desc_cache;
> -	vcpu->arch.mmu_pte_list_desc_cache.gfp_zero = __GFP_ZERO;
>  
>  	INIT_KVM_MMU_MEMORY_CACHE(&vcpu->arch.mmu_page_header_cache);
>  	vcpu->arch.mmu_page_header_cache.kmem_cache = mmu_page_header_cache;
> -	vcpu->arch.mmu_page_header_cache.gfp_zero = __GFP_ZERO;
>  
>  	INIT_KVM_MMU_MEMORY_CACHE(&vcpu->arch.mmu_shadow_page_cache);
> -	vcpu->arch.mmu_shadow_page_cache.gfp_zero = __GFP_ZERO;
>  	mutex_init(&vcpu->arch.mmu_shadow_page_cache_lock);
>  
>  	INIT_KVM_MMU_MEMORY_CACHE(&vcpu->arch.mmu_shadowed_info_cache);
> @@ -6138,14 +6135,11 @@ int kvm_mmu_init_vm(struct kvm *kvm)
>  
>  	INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_page_header_cache);
>  	kvm->arch.split_page_header_cache.kmem_cache = mmu_page_header_cache;
> -	kvm->arch.split_page_header_cache.gfp_zero = __GFP_ZERO;
>  
>  	INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_shadow_page_cache);
> -	kvm->arch.split_shadow_page_cache.gfp_zero = __GFP_ZERO;
>  
>  	INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_desc_cache);
>  	kvm->arch.split_desc_cache.kmem_cache = pte_list_desc_cache;
> -	kvm->arch.split_desc_cache.gfp_zero = __GFP_ZERO;
>  
>  	return 0;
>  }
> diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
> index 192516eeccac..5da7953532ce 100644
> --- a/include/linux/kvm_types.h
> +++ b/include/linux/kvm_types.h
> @@ -99,7 +99,9 @@ struct kvm_mmu_memory_cache {
>  	void **objects;
>  };
>  
> -#define KVM_MMU_MEMORY_CACHE_INIT() { }
> +#define KVM_MMU_MEMORY_CACHE_INIT() {	\
> +	.gfp_zero = __GFP_ZERO,		\
> +}
>  
>  #define KVM_MMU_MEMORY_CACHE(_name) \
>  		struct kvm_mmu_memory_cache _name = KVM_MMU_MEMORY_CACHE_INIT()
> -- 
> 2.40.0.rc0.216.gc4246ad0f0-goog
>