diff options
| author | Ben Gardon <bgardon@google.com> | 2021-05-18 20:34:14 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2021-06-17 20:09:27 +0300 |
| commit | d501f747ef5c0ac0c917f9a6781d04ae4ae39d63 (patch) | |
| tree | 4e083219aaff30031d8df1fb0463279ba0cba222 /arch/x86/kvm/mmu | |
| parent | e2209710ccc5d28d8b88c822d2f3e03b269a2856 (diff) | |
| download | linux-d501f747ef5c0ac0c917f9a6781d04ae4ae39d63.tar.xz | |
KVM: x86/mmu: Lazily allocate memslot rmaps
If the TDP MMU is in use, wait to allocate the rmaps until the shadow
MMU is actually used. (i.e. a nested VM is launched.) This saves memory
equal to 0.2% of guest memory in cases where the TDP MMU is used and
there are no nested guests involved.
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210518173414.450044-8-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/mmu')
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 14 | ||||
| -rw-r--r-- | arch/x86/kvm/mmu/tdp_mmu.c | 6 | ||||
| -rw-r--r-- | arch/x86/kvm/mmu/tdp_mmu.h | 4 |
3 files changed, 17 insertions, 7 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 2131f71577bc..aa9e77f406d9 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3312,6 +3312,10 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) } } + r = alloc_all_memslots_rmaps(vcpu->kvm); + if (r) + return r; + write_lock(&vcpu->kvm->mmu_lock); r = make_mmu_pages_available(vcpu); if (r < 0) @@ -5523,9 +5527,13 @@ void kvm_mmu_init_vm(struct kvm *kvm) { struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker; - kvm_mmu_init_tdp_mmu(kvm); - - kvm->arch.memslots_have_rmaps = true; + if (!kvm_mmu_init_tdp_mmu(kvm)) + /* + * No smp_load/store wrappers needed here as we are in + * VM init and there cannot be any memslots / other threads + * accessing this struct kvm yet. + */ + kvm->arch.memslots_have_rmaps = true; node->track_write = kvm_mmu_pte_write; node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot; diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 6b6dfcdcb179..cc13e001f3de 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -14,10 +14,10 @@ static bool __read_mostly tdp_mmu_enabled = false; module_param_named(tdp_mmu, tdp_mmu_enabled, bool, 0644); /* Initializes the TDP MMU for the VM, if enabled. */ -void kvm_mmu_init_tdp_mmu(struct kvm *kvm) +bool kvm_mmu_init_tdp_mmu(struct kvm *kvm) { if (!tdp_enabled || !READ_ONCE(tdp_mmu_enabled)) - return; + return false; /* This should not be changed for the lifetime of the VM. */ kvm->arch.tdp_mmu_enabled = true; @@ -25,6 +25,8 @@ void kvm_mmu_init_tdp_mmu(struct kvm *kvm) INIT_LIST_HEAD(&kvm->arch.tdp_mmu_roots); spin_lock_init(&kvm->arch.tdp_mmu_pages_lock); INIT_LIST_HEAD(&kvm->arch.tdp_mmu_pages); + + return true; } static __always_inline void kvm_lockdep_assert_mmu_lock_held(struct kvm *kvm, diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h index a861570fcd7c..f7a7990da11d 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.h +++ b/arch/x86/kvm/mmu/tdp_mmu.h @@ -81,12 +81,12 @@ int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, int *root_level); #ifdef CONFIG_X86_64 -void kvm_mmu_init_tdp_mmu(struct kvm *kvm); +bool kvm_mmu_init_tdp_mmu(struct kvm *kvm); void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm); static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return kvm->arch.tdp_mmu_enabled; } static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return sp->tdp_mmu_page; } #else -static inline void kvm_mmu_init_tdp_mmu(struct kvm *kvm) {} +static inline bool kvm_mmu_init_tdp_mmu(struct kvm *kvm) { return false; } static inline void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) {} static inline bool is_tdp_mmu_enabled(struct kvm *kvm) { return false; } static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return false; } |