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References: <20221222023457.1764-1-vipinsh@google.com> <20221222023457.1764-7-vipinsh@google.com>
 <Y64eAvm4JglT1au4@google.com>
In-Reply-To: <Y64eAvm4JglT1au4@google.com>
From:   David Matlack <dmatlack@google.com>
Date:   Thu, 29 Dec 2022 15:11:38 -0800
Message-ID: <CALzav=fGmy=YmpA6u=b0-p8zxnKbF2rt5mQUo-DWm2wYBU7dzA@mail.gmail.com>
Subject: Re: [Patch v3 6/9] KVM: Provide NUMA node support to kvm_mmu_memory_cache{}
To:     Vipin Sharma <vipinsh@google.com>
Cc:     seanjc@google.com, pbonzini@redhat.com, bgardon@google.com,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org
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On Thu, Dec 29, 2022 at 3:08 PM David Matlack <dmatlack@google.com> wrote:
>
> On Wed, Dec 21, 2022 at 06:34:54PM -0800, Vipin Sharma 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@google.com>
> > ---
> >  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);
>
> This is not any better than setting cache.node = NUMA_NO_NODE directly.
> Yes it's less lines of code, but it's harder to read (what does NULL
> mean here?), and every user of kvm_mmu_memory_cache still has to know to
> pass NUMA_NO_NODE.
>
> When I originally gave this suggestion, I intended to suggest that
> INIT_KVM_MMU_MEMORY_CACHE() provide just default initialization.
> Non-default initialization for gfp_zero, gfp_custom, kmem_cache, and
> node would remain as they are.
>
> Yes this adds some more lines, but keeps things readable, and doesn't
> every initialization site of kvm_mmu_memory_cache to know what to pass
> for gfp_zero, node, and kmem_cache. It only needs to set the fields
> *it* cares about.

And to offset the extra lines to call INIT_KVM_MMU_MEMORY_CACHE(), we
could finally invert the meaning of gfp_zero so that caches use
__GFP_ZERO by default. The majority of caches want __GFP_ZERO, so that
should cut down a bunch of lines.

>
> Here's what I mean specifically, based on INIT_LIST_HEAD. I don't think
> I got all the kvm_mmu_memory_cache users, but you get the point.
>
>
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 9c5573bc4614..0e138dcaf4d4 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -340,6 +340,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>         vcpu->arch.target = -1;
>         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;
>
>         /*
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 31d7fa4c7c14..f5fd78a4f084 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 };
> +       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);
>
> +       cache.gfp_zero = __GFP_ZERO;
> +
>         if (is_protected_kvm_enabled())
>                 return -EPERM;
>
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index 34b57e0be2ef..7915a5a2d104 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -351,10 +351,11 @@ int kvm_riscv_gstage_ioremap(struct kvm *kvm, gpa_t gpa,
>         int ret = 0;
>         unsigned long pfn;
>         phys_addr_t addr, end;
> -       struct kvm_mmu_memory_cache pcache = {
> -               .gfp_custom = (in_atomic) ? GFP_ATOMIC | __GFP_ACCOUNT : 0,
> -               .gfp_zero = __GFP_ZERO,
> -       };
> +       KVM_MMU_MEMORY_CACHE(pcache);
> +
> +       pcache.gfp_zero = __GFP_ZERO;
> +       if (in_atomic)
> +               pcache.gfp_custom = GFP_ATOMIC | __GFP_ACCOUNT;
>
>         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..3d73ab3ec9a4 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -161,6 +161,7 @@ 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_header_cache);
>         vcpu->arch.mmu_page_cache.gfp_zero = __GFP_ZERO;
>         bitmap_zero(vcpu->arch.isa, RISCV_ISA_EXT_MAX);
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 254bc46234e0..d4cd8e64cc03 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -5909,14 +5909,19 @@ int kvm_mmu_create(struct kvm_vcpu *vcpu)
>  {
>         int ret;
>
> +       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;
>
> +       INIT_KVM_MMU_MEMORY_CACHE(&vcpu->arch.mmu_shadowed_info_cache);
> +
>         vcpu->arch.mmu = &vcpu->arch.root_mmu;
>         vcpu->arch.walk_mmu = &vcpu->arch.root_mmu;
>
> @@ -6083,11 +6088,14 @@ 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);
>
> +       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;
>
> diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
> index 76de36e56cdf..eb7ff9afa5c7 100644
> --- a/include/linux/kvm_types.h
> +++ b/include/linux/kvm_types.h
> @@ -98,6 +98,17 @@ struct kvm_mmu_memory_cache {
>         int capacity;
>         void **objects;
>  };
> +
> +#define KVM_MMU_MEMORY_CACHE_INIT() (struct kvm_mmu_memory_cache) { \
> +}
> +
> +#define KVM_MMU_MEMORY_CACHE(_name) \
> +       struct kvm_mmu_memory_cache _name = KVM_MMU_MEMORY_CACHE_INIT()
> +
> +static inline void INIT_KVM_MMU_MEMORY_CACHE(struct kvm_mmu_memory_cache *cache)
> +{
> +       *cache = KVM_MMU_MEMORY_CACHE_INIT();
> +}
>  #endif
>
>  #define HALT_POLL_HIST_COUNT                   32
>
> > +
> >       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;
> > +
> >       /*
> >        * 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;                                         \
> > +})
> > +
> >  #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
> >