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| author |   Ben Gardon <bgardon@google.com> | 2021-05-18 10:34:14 -0700 |
|---|---|---|
| committer |   Paolo Bonzini <pbonzini@redhat.com> | 2021-06-17 13:09:27 -0400 |
| commit | d501f747ef5c0ac0c917f9a6781d04ae4ae39d63 (patch) | |
| tree | 4e083219aaff30031d8df1fb0463279ba0cba222 /arch/x86/kvm/mmu.h | |
| parent | KVM: x86/mmu: Skip rmap operations if rmaps not allocated (diff) | |
| download | linux-dev-d501f747ef5c0ac0c917f9a6781d04ae4ae39d63.tar.xz linux-dev-d501f747ef5c0ac0c917f9a6781d04ae4ae39d63.zip | |
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.h')
| -rw-r--r-- | arch/x86/kvm/mmu.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index af09c47b1aa2..9d8550af994c 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -234,7 +234,12 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm); static inline bool kvm_memslots_have_rmaps(struct kvm *kvm) { - return kvm->arch.memslots_have_rmaps; + /* + * Read memslot_have_rmaps before rmap pointers. Hence, threads reading + * memslots_have_rmaps in any lock context are guaranteed to see the + * pointers. Pairs with smp_store_release in alloc_all_memslots_rmaps. + */ + return smp_load_acquire(&kvm->arch.memslots_have_rmaps); } #endif |