KVM: x86/mmu: Add a field to control memslot rmap allocation

Add a field to control whether new memslots should have rmaps allocated
for them. As of this change, it's not safe to skip allocating rmaps, so
the field is always set to allocate rmaps. Future changes will make it
safe to operate without rmaps, using the TDP MMU. Then further changes
will allow the rmaps to be allocated lazily when needed for nested
oprtation.

No functional change expected.

Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210518173414.450044-6-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 9c7ced0..11798a9 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1124,6 +1124,12 @@ struct kvm_arch {
         */
        spinlock_t tdp_mmu_pages_lock;
 #endif /* CONFIG_X86_64 */
+
+       /*
+        * If set, rmaps have been allocated for all memslots and should be
+        * allocated for any newly created or modified memslots.
+        */
+       bool memslots_have_rmaps;
 };
 
 struct kvm_vm_stat {

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 66e4d09..64b3ee7 100644 (file)
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5511,6 +5511,8 @@ void kvm_mmu_init_vm(struct kvm *kvm)
 
        kvm_mmu_init_tdp_mmu(kvm);
 
+       kvm->arch.memslots_have_rmaps = true;
+
        node->track_write = kvm_mmu_pte_write;
        node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
        kvm_page_track_register_notifier(kvm, node);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5f66a59..11637fb 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10962,7 +10962,8 @@ static int memslot_rmap_alloc(struct kvm_memory_slot *slot,
        return 0;
 }
 
-static int kvm_alloc_memslot_metadata(struct kvm_memory_slot *slot,
+static int kvm_alloc_memslot_metadata(struct kvm *kvm,
+                                     struct kvm_memory_slot *slot,
                                      unsigned long npages)
 {
        int i, r;
@@ -10974,9 +10975,11 @@ static int kvm_alloc_memslot_metadata(struct kvm_memory_slot *slot,
         */
        memset(&slot->arch, 0, sizeof(slot->arch));
 
-       r = memslot_rmap_alloc(slot, npages);
-       if (r)
-               return r;
+       if (kvm->arch.memslots_have_rmaps) {
+               r = memslot_rmap_alloc(slot, npages);
+               if (r)
+                       return r;
+       }
 
        for (i = 1; i < KVM_NR_PAGE_SIZES; ++i) {
                struct kvm_lpage_info *linfo;
@@ -11047,7 +11050,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
                                enum kvm_mr_change change)
 {
        if (change == KVM_MR_CREATE || change == KVM_MR_MOVE)
-               return kvm_alloc_memslot_metadata(memslot,
+               return kvm_alloc_memslot_metadata(kvm, memslot,
                                                  mem->memory_size >> PAGE_SHIFT);
        return 0;
 }