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Date: Tue, 27 Dec 2022 11:42:56 -0800
From: Ben Gardon <bgardon@...gle.com>
To: Vipin Sharma <vipinsh@...gle.com>
Cc: seanjc@...gle.com, pbonzini@...hat.com, dmatlack@...gle.com,
kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Patch v3 8/9] KVM: x86/mmu: Make split_shadow_page_cache NUMA aware
On Wed, Dec 21, 2022 at 6:35 PM Vipin Sharma <vipinsh@...gle.com> wrote:
>
> Make split_shadow_page_cache NUMA aware and allocate page table's pages
> during the split based on the underlying physical page's NUMA node.
>
> Signed-off-by: Vipin Sharma <vipinsh@...gle.com>
> ---
> arch/x86/include/asm/kvm_host.h | 2 +-
> arch/x86/kvm/mmu/mmu.c | 50 ++++++++++++++++++---------------
> 2 files changed, 29 insertions(+), 23 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index b1f319ad6f89..7b3f36ae37a4 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1410,7 +1410,7 @@ struct kvm_arch {
> *
> * Protected by kvm->slots_lock.
> */
> - struct kvm_mmu_memory_cache split_shadow_page_cache;
> + struct kvm_mmu_memory_cache split_shadow_page_cache[MAX_NUMNODES];
> struct kvm_mmu_memory_cache split_page_header_cache;
>
> /*
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 511c6ef265ee..7454bfc49a51 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -6126,7 +6126,7 @@ static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
> int kvm_mmu_init_vm(struct kvm *kvm)
> {
> struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
> - int r;
> + int r, nid;
>
> INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
> INIT_LIST_HEAD(&kvm->arch.possible_nx_huge_pages);
> @@ -6145,8 +6145,9 @@ int kvm_mmu_init_vm(struct kvm *kvm)
> INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_page_header_cache,
> mmu_page_header_cache, NUMA_NO_NODE);
>
> - INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_shadow_page_cache,
> - NULL, NUMA_NO_NODE);
> + for_each_node(nid)
Again, assuming no one sets CONFIG_NODE_SHIFT to a ridiculous value,
it would probably be fine to initialize the entire array here since
that doesn't take any extra memory and we're not in a super hot path.
> + INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_shadow_page_cache[nid],
> + NULL, NUMA_NO_NODE);
> spin_lock_init(&kvm->arch.split_shadow_page_cache_lock);
>
> INIT_KVM_MMU_MEMORY_CACHE(&kvm->arch.split_desc_cache,
> @@ -6157,10 +6158,13 @@ int kvm_mmu_init_vm(struct kvm *kvm)
>
> static void mmu_free_vm_memory_caches(struct kvm *kvm)
> {
> + int nid;
> +
> kvm_mmu_free_memory_cache(&kvm->arch.split_desc_cache);
> kvm_mmu_free_memory_cache(&kvm->arch.split_page_header_cache);
> - mmu_free_sp_memory_cache(&kvm->arch.split_shadow_page_cache,
> - &kvm->arch.split_shadow_page_cache_lock);
> + for_each_node(nid)
Again, could just iterate over the whole array here.
> + mmu_free_sp_memory_cache(&kvm->arch.split_shadow_page_cache[nid],
> + &kvm->arch.split_shadow_page_cache_lock);
> }
>
> void kvm_mmu_uninit_vm(struct kvm *kvm)
> @@ -6269,7 +6273,7 @@ static inline bool need_topup(struct kvm_mmu_memory_cache *cache, int min)
> return kvm_mmu_memory_cache_nr_free_objects(cache) < min;
> }
>
> -static bool need_topup_split_caches_or_resched(struct kvm *kvm)
> +static bool need_topup_split_caches_or_resched(struct kvm *kvm, int nid)
> {
> if (need_resched() || rwlock_needbreak(&kvm->mmu_lock))
> return true;
> @@ -6281,10 +6285,10 @@ static bool need_topup_split_caches_or_resched(struct kvm *kvm)
> */
> return need_topup(&kvm->arch.split_desc_cache, SPLIT_DESC_CACHE_MIN_NR_OBJECTS) ||
> need_topup(&kvm->arch.split_page_header_cache, 1) ||
> - need_topup(&kvm->arch.split_shadow_page_cache, 1);
> + need_topup(&kvm->arch.split_shadow_page_cache[nid], 1);
> }
>
> -static int topup_split_caches(struct kvm *kvm)
> +static int topup_split_caches(struct kvm *kvm, int nid)
> {
> /*
> * Allocating rmap list entries when splitting huge pages for nested
> @@ -6314,18 +6318,21 @@ static int topup_split_caches(struct kvm *kvm)
> if (r)
> return r;
>
> - return mmu_topup_sp_memory_cache(&kvm->arch.split_shadow_page_cache,
> + return mmu_topup_sp_memory_cache(&kvm->arch.split_shadow_page_cache[nid],
> &kvm->arch.split_shadow_page_cache_lock,
> 1);
> }
>
> -static struct kvm_mmu_page *shadow_mmu_get_sp_for_split(struct kvm *kvm, u64 *huge_sptep)
> +static struct kvm_mmu_page *shadow_mmu_get_sp_for_split(struct kvm *kvm,
> + u64 *huge_sptep,
> + u64 huge_spte)
These can go on the same line.
> {
> struct kvm_mmu_page *huge_sp = sptep_to_sp(huge_sptep);
> struct shadow_page_caches caches = {};
> union kvm_mmu_page_role role;
> unsigned int access;
> gfn_t gfn;
> + int nid;
>
> gfn = kvm_mmu_page_get_gfn(huge_sp, spte_index(huge_sptep));
> access = kvm_mmu_page_get_access(huge_sp, spte_index(huge_sptep));
> @@ -6338,9 +6345,11 @@ static struct kvm_mmu_page *shadow_mmu_get_sp_for_split(struct kvm *kvm, u64 *hu
> */
> role = kvm_mmu_child_role(huge_sptep, /*direct=*/true, access);
>
> + nid = kvm_pfn_to_page_table_nid(spte_to_pfn(huge_spte));
> +
> /* Direct SPs do not require a shadowed_info_cache. */
> caches.page_header_cache = &kvm->arch.split_page_header_cache;
> - caches.shadow_page_cache = &kvm->arch.split_shadow_page_cache;
> + caches.shadow_page_cache = &kvm->arch.split_shadow_page_cache[nid];
> caches.shadow_page_cache_lock = &kvm->arch.split_shadow_page_cache_lock;
>
> /* Safe to pass NULL for vCPU since requesting a direct SP. */
> @@ -6360,7 +6369,7 @@ static void shadow_mmu_split_huge_page(struct kvm *kvm,
> gfn_t gfn;
> int index;
>
> - sp = shadow_mmu_get_sp_for_split(kvm, huge_sptep);
> + sp = shadow_mmu_get_sp_for_split(kvm, huge_sptep, huge_spte);
>
> for (index = 0; index < SPTE_ENT_PER_PAGE; index++) {
> sptep = &sp->spt[index];
> @@ -6398,7 +6407,7 @@ static int shadow_mmu_try_split_huge_page(struct kvm *kvm,
> u64 *huge_sptep)
> {
> struct kvm_mmu_page *huge_sp = sptep_to_sp(huge_sptep);
> - int level, r = 0;
> + int level, r = 0, nid;
> gfn_t gfn;
> u64 spte;
>
> @@ -6406,13 +6415,14 @@ static int shadow_mmu_try_split_huge_page(struct kvm *kvm,
> gfn = kvm_mmu_page_get_gfn(huge_sp, spte_index(huge_sptep));
> level = huge_sp->role.level;
> spte = *huge_sptep;
> + nid = kvm_pfn_to_page_table_nid(spte_to_pfn(spte));
>
> if (kvm_mmu_available_pages(kvm) <= KVM_MIN_FREE_MMU_PAGES) {
> r = -ENOSPC;
> goto out;
> }
>
> - if (need_topup_split_caches_or_resched(kvm)) {
> + if (need_topup_split_caches_or_resched(kvm, nid)) {
> write_unlock(&kvm->mmu_lock);
> cond_resched();
> /*
> @@ -6420,7 +6430,7 @@ static int shadow_mmu_try_split_huge_page(struct kvm *kvm,
> * rmap iterator should be restarted because the MMU lock was
> * dropped.
> */
> - r = topup_split_caches(kvm) ?: -EAGAIN;
> + r = topup_split_caches(kvm, nid) ?: -EAGAIN;
> write_lock(&kvm->mmu_lock);
> goto out;
> }
> @@ -6709,17 +6719,15 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
> }
>
> static unsigned long mmu_shrink_cache(struct kvm_mmu_memory_cache *cache,
> - int cache_count,
> spinlock_t *cache_lock)
> {
> unsigned long freed = 0;
> int nid;
>
> spin_lock(cache_lock);
> - for (nid = 0; nid < cache_count; nid++) {
> - if (node_online(nid) && cache[nid].nobjs)
> + for_each_online_node(nid)
> + if (cache[nid].nobjs)
> freed += kvm_mmu_empty_memory_cache(&cache[nid]);
> - }
> spin_unlock(cache_lock);
> return freed;
> }
> @@ -6741,8 +6749,7 @@ mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
> first_kvm = kvm;
> list_move_tail(&kvm->vm_list, &vm_list);
>
> - freed += mmu_shrink_cache(&kvm->arch.split_shadow_page_cache,
> - 1,
> + freed += mmu_shrink_cache(kvm->arch.split_shadow_page_cache,
> &kvm->arch.split_shadow_page_cache_lock);
>
> if (freed >= sc->nr_to_scan)
> @@ -6750,7 +6757,6 @@ mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
>
> kvm_for_each_vcpu(i, vcpu, kvm) {
> freed += mmu_shrink_cache(vcpu->arch.mmu_shadow_page_cache,
> - MAX_NUMNODES,
> &vcpu->arch.mmu_shadow_page_cache_lock);
> }
>
> --
> 2.39.0.314.g84b9a713c41-goog
>
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