Re: [Patch v2 2/2] KVM: x86/mmu: Allocate page table pages on NUMA node of underlying pages

From: Ben Gardon
Date: Mon Dec 05 2022 - 13:17:25 EST

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In reply to: Vipin Sharma: "[Patch v2 2/2] KVM: x86/mmu: Allocate page table pages on NUMA node of underlying pages"
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On Thu, Dec 1, 2022 at 11:57 AM Vipin Sharma <vipinsh@xxxxxxxxxx> wrote:
>
> Page table pages of a VM are currently allocated based on the current
> task's NUMA node or its mempolicy. This can cause suboptimal remote
> accesses by the vCPU if it is accessing physical pages local to its NUMA
> node but the page table pages mapping those physcal pages were created
> by some other vCPU which was on different NUMA node or had different
> policy.
>
> Allocate page table pages on the same NUMA node where underlying
> physical page exists. Page table at level 5, 4, and 3 might not end up
> on the same NUMA node as they can span multiple NUMA nodes.
>
> Signed-off-by: Vipin Sharma <vipinsh@xxxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 4 +-
> arch/x86/kvm/mmu.h | 1 -
> arch/x86/kvm/mmu/mmu.c | 109 ++++++++++++++++++++++----------
> arch/x86/kvm/mmu/paging_tmpl.h | 4 +-
> arch/x86/kvm/mmu/tdp_mmu.c | 16 +++--
> include/linux/kvm_host.h | 2 +
> include/linux/kvm_types.h | 2 +
> virt/kvm/kvm_main.c | 7 +-
> 8 files changed, 101 insertions(+), 44 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 283cbb83d6ae..8a0293326abc 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -782,7 +782,7 @@ struct kvm_vcpu_arch {
> struct kvm_mmu *walk_mmu;
>
> struct kvm_mmu_memory_cache mmu_pte_list_desc_cache;
> - struct kvm_mmu_memory_cache mmu_shadow_page_cache;
> + struct kvm_mmu_memory_cache mmu_shadow_page_cache[MAX_NUMNODES];
> struct kvm_mmu_memory_cache mmu_shadowed_info_cache;
> struct kvm_mmu_memory_cache mmu_page_header_cache;
>
> @@ -1415,7 +1415,7 @@ 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.h b/arch/x86/kvm/mmu.h
> index c960fb096e5c..6bdaacb6faa0 100644
> --- a/arch/x86/kvm/mmu.h
> +++ b/arch/x86/kvm/mmu.h
> @@ -119,7 +119,6 @@ void kvm_mmu_unload(struct kvm_vcpu *vcpu);
> void kvm_mmu_free_obsolete_roots(struct kvm_vcpu *vcpu);
> void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu);
> void kvm_mmu_sync_prev_roots(struct kvm_vcpu *vcpu);
> -void *kvm_mmu_get_free_page(int nid, gfp_t gfp);
>
> static inline int kvm_mmu_reload(struct kvm_vcpu *vcpu)
> {
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 0554dfc55553..ff7b17af8ab8 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -648,31 +648,43 @@ static void walk_shadow_page_lockless_end(struct kvm_vcpu *vcpu)
>
> static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu, bool maybe_indirect)
> {
> - int r;
> + int r, i;

Nit: nid or node or node_id would be more descriptive than just i.

>
> /* 1 rmap, 1 parent PTE per level, and the prefetched rmaps. */
> r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache,
> 1 + PT64_ROOT_MAX_LEVEL + PTE_PREFETCH_NUM);
> if (r)
> return r;
> - r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_shadow_page_cache,
> - PT64_ROOT_MAX_LEVEL);
> - if (r)
> - return r;
> +
> + for (i = 0; i < MAX_NUMNODES; i++) {
> + if (node_online(i)) {
> + r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_shadow_page_cache[i],
> + PT64_ROOT_MAX_LEVEL);
> + if (r)
> + return r;
> + }
> + }
> +

Nice, I was worried about wasting cache memory we were never going to
use, but this works great to at least ensure we're not allocating
cached memory for nodes that don't exist.

> if (maybe_indirect) {
> r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_shadowed_info_cache,
> PT64_ROOT_MAX_LEVEL);
> if (r)
> return r;
> }
> +
> return kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache,
> PT64_ROOT_MAX_LEVEL);
> }
>
> static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
> {
> + int i;
> +
> kvm_mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache);
> - kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadow_page_cache);
> +
> + for (i = 0; i < MAX_NUMNODES; i++)
> + kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadow_page_cache[i]);
> +
> kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadowed_info_cache);
> kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache);
> }
> @@ -2203,13 +2215,17 @@ static struct kvm_mmu_page *__kvm_mmu_get_shadow_page(struct kvm *kvm,
>
> static struct kvm_mmu_page *kvm_mmu_get_shadow_page(struct kvm_vcpu *vcpu,
> gfn_t gfn,
> - union kvm_mmu_page_role role)
> + union kvm_mmu_page_role role,
> + int nid)
> {
> - struct shadow_page_caches caches = {
> - .page_header_cache = &vcpu->arch.mmu_page_header_cache,
> - .shadow_page_cache = &vcpu->arch.mmu_shadow_page_cache,
> - .shadowed_info_cache = &vcpu->arch.mmu_shadowed_info_cache,
> - };
> + struct shadow_page_caches caches;
> +
> + if (nid == NUMA_NO_NODE)
> + nid = numa_mem_id();
> +
> + caches.page_header_cache = &vcpu->arch.mmu_page_header_cache;
> + caches.shadow_page_cache = &vcpu->arch.mmu_shadow_page_cache[nid];
> + caches.shadowed_info_cache = &vcpu->arch.mmu_shadowed_info_cache;
>
> return __kvm_mmu_get_shadow_page(vcpu->kvm, vcpu, &caches, gfn, role);
> }
> @@ -2262,15 +2278,19 @@ static union kvm_mmu_page_role kvm_mmu_child_role(u64 *sptep, bool direct,
>
> static struct kvm_mmu_page *kvm_mmu_get_child_sp(struct kvm_vcpu *vcpu,
> u64 *sptep, gfn_t gfn,
> - bool direct, unsigned int access)
> + bool direct, unsigned int access,
> + kvm_pfn_t pfn)
> {
> union kvm_mmu_page_role role;
> + int nid;
>
> if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep))
> return ERR_PTR(-EEXIST);
>
> role = kvm_mmu_child_role(sptep, direct, access);
> - return kvm_mmu_get_shadow_page(vcpu, gfn, role);
> + nid = kvm_pfn_to_refcounted_page_nid(pfn);
> +
> + return kvm_mmu_get_shadow_page(vcpu, gfn, role, nid);
> }
>
> static void shadow_walk_init_using_root(struct kvm_shadow_walk_iterator *iterator,
> @@ -3153,7 +3173,8 @@ static int __direct_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> if (it.level == fault->goal_level)
> break;
>
> - sp = kvm_mmu_get_child_sp(vcpu, it.sptep, base_gfn, true, ACC_ALL);
> + sp = kvm_mmu_get_child_sp(vcpu, it.sptep, base_gfn, true,
> + ACC_ALL, fault->pfn);
> if (sp == ERR_PTR(-EEXIST))
> continue;
>
> @@ -3579,7 +3600,7 @@ static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, int quadrant,
> WARN_ON_ONCE(quadrant && !role.has_4_byte_gpte);
> WARN_ON_ONCE(role.direct && role.has_4_byte_gpte);
>
> - sp = kvm_mmu_get_shadow_page(vcpu, gfn, role);
> + sp = kvm_mmu_get_shadow_page(vcpu, gfn, role, NUMA_NO_NODE);
> ++sp->root_count;
>
> return __pa(sp->spt);
> @@ -5853,15 +5874,20 @@ static int __kvm_mmu_create(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
>
> int kvm_mmu_create(struct kvm_vcpu *vcpu)
> {
> - int ret;
> + int ret, i;
>
> vcpu->arch.mmu_pte_list_desc_cache.kmem_cache = pte_list_desc_cache;
> vcpu->arch.mmu_pte_list_desc_cache.gfp_zero = __GFP_ZERO;
> + vcpu->arch.mmu_pte_list_desc_cache.node = 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;
> + vcpu->arch.mmu_page_header_cache.node = NUMA_NO_NODE;
>
> - vcpu->arch.mmu_shadow_page_cache.gfp_zero = __GFP_ZERO;
> + for (i = 0; i < MAX_NUMNODES; i++) {
> + vcpu->arch.mmu_shadow_page_cache[i].gfp_zero = __GFP_ZERO;
> + vcpu->arch.mmu_shadow_page_cache[i].node = i;
> + }
>
> vcpu->arch.mmu = &vcpu->arch.root_mmu;
> vcpu->arch.walk_mmu = &vcpu->arch.root_mmu;
> @@ -6012,7 +6038,7 @@ 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, i;
>
> INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
> INIT_LIST_HEAD(&kvm->arch.zapped_obsolete_pages);
> @@ -6029,20 +6055,29 @@ int kvm_mmu_init_vm(struct kvm *kvm)
>
> kvm->arch.split_page_header_cache.kmem_cache = mmu_page_header_cache;
> kvm->arch.split_page_header_cache.gfp_zero = __GFP_ZERO;
> + kvm->arch.split_page_header_cache.node = NUMA_NO_NODE;
> +
> + for (i = 0; i < MAX_NUMNODES; i++) {
> + kvm->arch.split_shadow_page_cache[i].gfp_zero = __GFP_ZERO;
> + kvm->arch.split_shadow_page_cache[i].node = i;
> + }
>
> - kvm->arch.split_shadow_page_cache.gfp_zero = __GFP_ZERO;
>
> kvm->arch.split_desc_cache.kmem_cache = pte_list_desc_cache;
> kvm->arch.split_desc_cache.gfp_zero = __GFP_ZERO;
> + kvm->arch.split_desc_cache.node = NUMA_NO_NODE;
>
> return 0;
> }
>
> static void mmu_free_vm_memory_caches(struct kvm *kvm)
> {
> + int i;
> +
> kvm_mmu_free_memory_cache(&kvm->arch.split_desc_cache);
> kvm_mmu_free_memory_cache(&kvm->arch.split_page_header_cache);
> - kvm_mmu_free_memory_cache(&kvm->arch.split_shadow_page_cache);
> + for (i = 0; i < MAX_NUMNODES; i++)
> + kvm_mmu_free_memory_cache(&kvm->arch.split_shadow_page_cache[i]);
> }
>
> void kvm_mmu_uninit_vm(struct kvm *kvm)
> @@ -6150,7 +6185,7 @@ 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;
> @@ -6162,10 +6197,10 @@ 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
> @@ -6195,16 +6230,19 @@ static int topup_split_caches(struct kvm *kvm)
> if (r)
> return r;
>
> - return kvm_mmu_topup_memory_cache(&kvm->arch.split_shadow_page_cache, 1);
> + return kvm_mmu_topup_memory_cache(&kvm->arch.split_shadow_page_cache[nid], 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)
> {
> 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));
> @@ -6217,9 +6255,13 @@ 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_refcounted_page_nid(spte_to_pfn(huge_spte));
> + if (nid == NUMA_NO_NODE)
> + nid = numa_mem_id();
> +
> /* 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];
>
> /* Safe to pass NULL for vCPU since requesting a direct SP. */
> return __kvm_mmu_get_shadow_page(kvm, NULL, &caches, gfn, role);
> @@ -6238,7 +6280,7 @@ 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];
> @@ -6276,7 +6318,7 @@ 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;
>
> @@ -6284,13 +6326,16 @@ 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_refcounted_page_nid(spte_to_pfn(spte));
> + if (nid == NUMA_NO_NODE)
> + nid = numa_mem_id();
>
> 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();
> /*
> @@ -6298,7 +6343,7 @@ 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;
> }
> @@ -6988,7 +7033,7 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
> kthread_stop(kvm->arch.nx_huge_page_recovery_thread);
> }
>
> -void *kvm_mmu_get_free_page(int nid, gfp_t gfp)
> +void *kvm_arch_mmu_get_free_page(int nid, gfp_t gfp)
> {
> struct page *spt_page;
> void *address = NULL;
> diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
> index 0f6455072055..1b1039a1b178 100644
> --- a/arch/x86/kvm/mmu/paging_tmpl.h
> +++ b/arch/x86/kvm/mmu/paging_tmpl.h
> @@ -652,7 +652,7 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
> table_gfn = gw->table_gfn[it.level - 2];
> access = gw->pt_access[it.level - 2];
> sp = kvm_mmu_get_child_sp(vcpu, it.sptep, table_gfn,
> - false, access);
> + false, access, fault->pfn);
>
> if (sp != ERR_PTR(-EEXIST)) {
> /*
> @@ -708,7 +708,7 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
> validate_direct_spte(vcpu, it.sptep, direct_access);
>
> sp = kvm_mmu_get_child_sp(vcpu, it.sptep, base_gfn,
> - true, direct_access);
> + true, direct_access, fault->pfn);
> if (sp == ERR_PTR(-EEXIST))
> continue;
>
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 1607afbfcc0b..be0763e6b058 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -270,12 +270,15 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
> kvm_mmu_page_as_id(_root) != _as_id) { \
> } else
>
> -static struct kvm_mmu_page *tdp_mmu_alloc_sp(struct kvm_vcpu *vcpu)
> +static struct kvm_mmu_page *tdp_mmu_alloc_sp(struct kvm_vcpu *vcpu, int nid)
> {
> struct kvm_mmu_page *sp;
>
> + if (nid == NUMA_NO_NODE)
> + nid = numa_mem_id();
> +
> sp = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
> - sp->spt = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
> + sp->spt = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache[nid]);
>
> return sp;
> }
> @@ -327,7 +330,7 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
> goto out;
> }
>
> - root = tdp_mmu_alloc_sp(vcpu);
> + root = tdp_mmu_alloc_sp(vcpu, NUMA_NO_NODE);
> tdp_mmu_init_sp(root, NULL, 0, role);
>
> refcount_set(&root->tdp_mmu_root_count, 1);
> @@ -1159,7 +1162,7 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> struct kvm *kvm = vcpu->kvm;
> struct tdp_iter iter;
> struct kvm_mmu_page *sp;
> - int ret = RET_PF_RETRY;
> + int ret = RET_PF_RETRY, nid;
>
> kvm_mmu_hugepage_adjust(vcpu, fault);
>
> @@ -1188,11 +1191,12 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> !is_large_pte(iter.old_spte))
> continue;
>
> + nid = kvm_pfn_to_refcounted_page_nid(fault->pfn);
> /*
> * The SPTE is either non-present or points to a huge page that
> * needs to be split.
> */
> - sp = tdp_mmu_alloc_sp(vcpu);
> + sp = tdp_mmu_alloc_sp(vcpu, nid);
> tdp_mmu_init_child_sp(sp, &iter);
>
> sp->nx_huge_page_disallowed = fault->huge_page_disallowed;
> @@ -1423,7 +1427,7 @@ static struct kvm_mmu_page *__tdp_mmu_alloc_sp_for_split(int nid, gfp_t gfp)
> if (!sp)
> return NULL;
>
> - sp->spt = kvm_mmu_get_free_page(nid, gfp);
> + sp->spt = kvm_arch_mmu_get_free_page(nid, gfp);
>
> if (!sp->spt) {
> kmem_cache_free(mmu_page_header_cache, sp);
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 558ded73f660..07674955460b 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1374,6 +1374,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu, bool usermode_vcpu_not_eligible);
>
> void kvm_flush_remote_tlbs(struct kvm *kvm);
>
> +void *kvm_arch_mmu_get_free_page(int nid, gfp_t gfp);
> +
> #ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE
> int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min);
> int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity, int min);
> diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
> index 3ca3db020e0e..cb627cf1b4e1 100644
> --- a/include/linux/kvm_types.h
> +++ b/include/linux/kvm_types.h
> @@ -96,6 +96,8 @@ 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
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 1782c4555d94..4d59c9d48277 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -384,6 +384,11 @@ static void kvm_flush_shadow_all(struct kvm *kvm)
> kvm_arch_guest_memory_reclaimed(kvm);
> }
>
> +void * __weak kvm_arch_mmu_get_free_page(int nid, gfp_t gfp_flags)
> +{
> + return (void *)__get_free_page(gfp_flags);
> +}
> +

Rather than making this __weak, you could use #ifdef CONFIG_NUMA to
just put all the code in the arch-neutral function.

> #ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE
> static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc,
> gfp_t gfp_flags)
> @@ -393,7 +398,7 @@ static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc,
> if (mc->kmem_cache)
> return kmem_cache_alloc(mc->kmem_cache, gfp_flags);
> else
> - return (void *)__get_free_page(gfp_flags);
> + return kvm_arch_mmu_get_free_page(mc->node, gfp_flags);
> }
>
> int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity, int min)
> --
> 2.39.0.rc0.267.gcb52ba06e7-goog
>

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