Re: [PATCH v2 11/20] KVM: selftests: Initialize vm->memslots[] with invalid memslots during creation

Initialize vm->memslots[] with an invalid memslots value during very
initial VM creation so that failure to configure the core memory regions
generates an immediate assert instead of potential weirdness, e.g. if slot0
is coincidentally valid.  This will also allow hardening the region APIs to
guard overriding a region's memslot multiple times.

Tested-by: Itaru Kitayama <redacted>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 tools/testing/selftests/kvm/include/kvm_util.h  | 2 ++
 tools/testing/selftests/kvm/lib/kvm_util.c      | 5 +++++
 tools/testing/selftests/kvm/lib/x86/processor.c | 5 ++++-
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index c56f342b16fd..304ef6af3268 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h

@@ -33,6 +33,8 @@
 
 #define NSEC_PER_SEC 1000000000L
 
+#define KVM_INVALID_MEMSLOT UINT_MAX
+
 struct userspace_mem_region {
 	struct kvm_userspace_memory_region2 region;
 	struct sparsebit *unused_phy_pages;

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index ce0d8fba4624..56df5b1d9c79 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c

@@ -288,6 +288,7 @@ __weak void vm_populate_gva_bitmap(struct kvm_vm *vm)
 struct kvm_vm *____vm_create(struct vm_shape shape)
 {
 	struct kvm_vm *vm;
+	int i;
 
 	vm = calloc(1, sizeof(*vm));
 	TEST_ASSERT(vm != NULL, "Insufficient Memory");

@@ -296,6 +297,8 @@ struct kvm_vm *____vm_create(struct vm_shape shape)
 	vm->regions.gpa_tree = RB_ROOT;
 	vm->regions.hva_tree = RB_ROOT;
 	hash_init(vm->regions.slot_hash);
+	for (i = 0; i < NR_MEM_REGIONS; i++)
+		vm->memslots[i] = KVM_INVALID_MEMSLOT;
 
 	vm->mode = shape.mode;
 	vm->type = shape.type;

@@ -1190,6 +1193,8 @@ memslot2region(struct kvm_vm *vm, u32 memslot)
 {
 	struct userspace_mem_region *region;
 
+	TEST_ASSERT(memslot != KVM_INVALID_MEMSLOT, "vm->memslots[] unpopulated?");
+
 	hash_for_each_possible(vm->regions.slot_hash, region, slot_node,
 			       memslot)
 		if (region->region.slot == memslot)

diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
index d31fa81ea075..ea5fa59888af 100644
--- a/tools/testing/selftests/kvm/lib/x86/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86/processor.c

@@ -529,7 +529,10 @@ void tdp_identity_map_default_memslots(struct kvm_vm *vm)
 
 	/* Only memslot 0 is mapped here, ensure it's the only one being used */
 	for (s = 0; s < NR_MEM_REGIONS; s++)
-		TEST_ASSERT_EQ(vm->memslots[s], 0);
+		TEST_ASSERT(!vm->memslots[s] ||
+			    vm->memslots[s] == KVM_INVALID_MEMSLOT,
+			    "Unhandled memslot '%u' for type '%u'",
+			    vm->memslots[s], s);
 
 	i = (region->region.guest_phys_addr >> vm->page_shift) - 1;
 	last = i + (region->region.memory_size >> vm->page_shift);

-- 
2.55.0.966.g6673acef38-goog