Re: [Patch v3 6/9] KVM: Provide NUMA node support to kvm_mmu_memory_cache{}

[Ben Gardon]

On Wed, Dec 21, 2022 at 6:35 PM Vipin Sharma <vipinsh@xxxxxxxxxx> wrote:
>
> Add 'node' variable in kvm_mmu_memory_cache{} to denote which NUMA node
> this cache should allocate memory from. Default initialize to
> NUMA_NO_NODE in all architectures.
>
> Signed-off-by: Vipin Sharma <vipinsh@xxxxxxxxxx>
> ---
>  arch/arm64/kvm/arm.c      |  2 +-
>  arch/arm64/kvm/mmu.c      |  4 +++-
>  arch/mips/kvm/mips.c      |  2 ++
>  arch/riscv/kvm/mmu.c      |  2 +-
>  arch/riscv/kvm/vcpu.c     |  2 +-
>  arch/x86/kvm/mmu/mmu.c    | 22 ++++++++++++----------
>  include/linux/kvm_host.h  |  6 ++++++
>  include/linux/kvm_types.h |  2 ++
>  8 files changed, 28 insertions(+), 14 deletions(-)
>
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 9c5573bc4614..52a41f4532e2 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -340,7 +340,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>         vcpu->arch.target = -1;
>         bitmap_zero(vcpu->arch.features, KVM_VCPU_MAX_FEATURES);
>
> -       vcpu->arch.mmu_page_cache.gfp_zero = __GFP_ZERO;
> +       INIT_KVM_MMU_MEMORY_CACHE(&vcpu->arch.mmu_page_cache, NULL, NUMA_NO_NODE);
>
>         /*
>          * 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 31d7fa4c7c14..bd07155e17fa 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -894,12 +894,14 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
>  {
>         phys_addr_t addr;
>         int ret = 0;
> -       struct kvm_mmu_memory_cache cache = { .gfp_zero = __GFP_ZERO };
> +       struct kvm_mmu_memory_cache cache;
>         struct kvm_pgtable *pgt = kvm->arch.mmu.pgt;
>         enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_DEVICE |
>                                      KVM_PGTABLE_PROT_R |
>                                      (writable ? KVM_PGTABLE_PROT_W : 0);
>
> +       INIT_KVM_MMU_MEMORY_CACHE(&cache, NULL, NUMA_NO_NODE);
> +
>         if (is_protected_kvm_enabled())
>                 return -EPERM;
>
> diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
> index a25e0b73ee70..b017c29a9340 100644
> --- a/arch/mips/kvm/mips.c
> +++ b/arch/mips/kvm/mips.c
> @@ -304,6 +304,8 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>                      HRTIMER_MODE_REL);
>         vcpu->arch.comparecount_timer.function = kvm_mips_comparecount_wakeup;
>
> +       vcpu->arch.mmu_page_cache.node = NUMA_NO_NODE;
> +

It looks weird to have MIPS not using the initialization MACRO. Should
it just have a GFP_ZERO parameter?

>         /*
>          * Allocate space for host mode exception handlers that handle
>          * guest mode exits
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index 34b57e0be2ef..119de4520cc6 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -353,9 +353,9 @@ int kvm_riscv_gstage_ioremap(struct kvm *kvm, gpa_t gpa,
>         phys_addr_t addr, end;
>         struct kvm_mmu_memory_cache pcache = {
>                 .gfp_custom = (in_atomic) ? GFP_ATOMIC | __GFP_ACCOUNT : 0,
> -               .gfp_zero = __GFP_ZERO,
>         };
>
> +       INIT_KVM_MMU_MEMORY_CACHE(&pcache, NULL, NUMA_NO_NODE);
>         end = (gpa + size + PAGE_SIZE - 1) & PAGE_MASK;
>         pfn = __phys_to_pfn(hpa);
>
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index 7c08567097f0..189b14feb365 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -161,7 +161,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>
>         /* Mark this VCPU never ran */
>         vcpu->arch.ran_atleast_once = false;
> -       vcpu->arch.mmu_page_cache.gfp_zero = __GFP_ZERO;
> +       INIT_KVM_MMU_MEMORY_CACHE(&vcpu->arch.mmu_page_cache, NULL, NUMA_NO_NODE);
>         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 6f6a10d7a871..23a3b82b2384 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5954,13 +5954,14 @@ int kvm_mmu_create(struct kvm_vcpu *vcpu)
>  {
>         int ret;
>
> -       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_pte_list_desc_cache,
> +                                 pte_list_desc_cache, NUMA_NO_NODE);
>
> -       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_page_header_cache,
> +                                 mmu_page_header_cache, NUMA_NO_NODE);
>
> -       vcpu->arch.mmu_shadow_page_cache.gfp_zero = __GFP_ZERO;
> +       INIT_KVM_MMU_MEMORY_CACHE(&vcpu->arch.mmu_shadow_page_cache,
> +                                 NULL, NUMA_NO_NODE);
>         spin_lock_init(&vcpu->arch.mmu_shadow_page_cache_lock);
>
>         vcpu->arch.mmu = &vcpu->arch.root_mmu;
> @@ -6124,14 +6125,15 @@ int kvm_mmu_init_vm(struct kvm *kvm)
>         node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
>         kvm_page_track_register_notifier(kvm, node);
>
> -       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_page_header_cache,
> +                                 mmu_page_header_cache, NUMA_NO_NODE);
>
> -       kvm->arch.split_shadow_page_cache.gfp_zero = __GFP_ZERO;
> +       INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_shadow_page_cache,
> +                                 NULL, NUMA_NO_NODE);
>         spin_lock_init(&kvm->arch.split_shadow_page_cache_lock);
>
> -       kvm->arch.split_desc_cache.kmem_cache = pte_list_desc_cache;
> -       kvm->arch.split_desc_cache.gfp_zero = __GFP_ZERO;
> +       INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_desc_cache,
> +                                 pte_list_desc_cache, NUMA_NO_NODE);
>
>         return 0;
>  }
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index a262e15ebd19..719687a37ef7 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2302,4 +2302,10 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr)
>  /* Max number of entries allowed for each kvm dirty ring */
>  #define  KVM_DIRTY_RING_MAX_ENTRIES  65536
>
> +#define INIT_KVM_MMU_MEMORY_CACHE(_cache, _kmem_cache, _node) ({       \
> +       (_cache)->kmem_cache = _kmem_cache;                             \
> +       (_cache)->gfp_zero = __GFP_ZERO;                                \
> +       (_cache)->node = _node;                                         \
> +})
> +

Given that this initialization is probably not happening in a super
hot path, is there any downside to just using a function for the
initialization?

>  #endif
> diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
> index 76de36e56cdf..9c70ce95e51f 100644
> --- a/include/linux/kvm_types.h
> +++ b/include/linux/kvm_types.h
> @@ -97,6 +97,8 @@ struct kvm_mmu_memory_cache {
>         struct kmem_cache *kmem_cache;
>         int capacity;
>         void **objects;
> +       /* Node on which memory should be allocated by default */
> +       int node;
>  };
>  #endif
>
> --
> 2.39.0.314.g84b9a713c41-goog
>