[PATCH v3 09/17] KVM: arm64: Add selftests for the pKVM heap allocator

[Vincent Donnefort <vdonnefort@google.com>]

Introduce a comprehensive runtime selftest for the pKVM hypervisor heap
allocator, executed during init when CONFIG_NVHE_EL2_DEBUG is enabled.

The selftest runs entirely at EL2 and exercises allocator's core
mechanisms:

  * over-sized allocations
  * basic allocation and alignment
  * chunk recycling, splitting, merging
  * memory reclaiming
  * memory topup

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 0c3126179704..08466f608d1f 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -92,6 +92,7 @@ enum __kvm_host_smccc_func {
 	__KVM_HOST_SMCCC_FUNC___pkvm_hyp_topup,
 	__KVM_HOST_SMCCC_FUNC___pkvm_hyp_reclaim,
 	__KVM_HOST_SMCCC_FUNC___pkvm_hyp_reclaimable,
+	__KVM_HOST_SMCCC_FUNC___pkvm_hyp_alloc_selftest,
 
 	MARKER(__KVM_HOST_SMCCC_FUNC_PKVM_ONLY),
 
diff --git a/arch/arm64/include/asm/kvm_pkvm.h b/arch/arm64/include/asm/kvm_pkvm.h
index 99daa985856f..73c8881e14ec 100644
--- a/arch/arm64/include/asm/kvm_pkvm.h
+++ b/arch/arm64/include/asm/kvm_pkvm.h
@@ -19,8 +19,10 @@
 
 enum pkvm_topup_id {
 	PKVM_TOPUP_HYP_ALLOC,
+	PKVM_TOPUP_HYP_ALLOC_SELFTEST,
 };
 
+void pkvm_selftests(void);
 int pkvm_init_host_vm(struct kvm *kvm, unsigned long type);
 int pkvm_create_hyp_vm(struct kvm *kvm);
 bool pkvm_hyp_vm_is_created(struct kvm *kvm);
@@ -206,6 +208,7 @@ struct pkvm_mapping {
 enum pkvm_hyp_req_type {
 	PKVM_HYP_NO_REQ = 0,
 	PKVM_HYP_REQ_HYP_ALLOC,
+	PKVM_HYP_REQ_HYP_ALLOC_SELFTEST,
 	__PKVM_HYP_REQ_TYPE_MAX,
 };
 
@@ -233,6 +236,7 @@ static inline size_t pkvm_hyp_req_arg_size(u8 type)
 	case PKVM_HYP_NO_REQ:
 		return 0;
 	case PKVM_HYP_REQ_HYP_ALLOC:
+	case PKVM_HYP_REQ_HYP_ALLOC_SELFTEST:
 		return sizeof(req->mem);
 	default:
 		WARN_ON(1);
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 50adfff75be8..750862705a70 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -2883,6 +2883,8 @@ static int __init init_hyp_mode(void)
 			kvm_err("Failed to init hyp memory protection\n");
 			goto out_err;
 		}
+
+		pkvm_selftests();
 	}
 
 	return 0;
diff --git a/arch/arm64/kvm/hyp/include/nvhe/alloc.h b/arch/arm64/kvm/hyp/include/nvhe/alloc.h
index 8f87a63f8946..329250dad6f6 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/alloc.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/alloc.h
@@ -14,4 +14,11 @@ int hyp_alloc_init(size_t size);
 int hyp_alloc_topup(struct kvm_hyp_memcache *host_mc);
 unsigned long hyp_alloc_reclaimable(void);
 void hyp_alloc_reclaim(struct kvm_hyp_memcache *host_mc, unsigned long target);
+
+#ifdef CONFIG_NVHE_EL2_DEBUG
+int hyp_allocator_selftest(void);
+u32 hyp_alloc_selftest_topup_needed(void);
+int hyp_alloc_selftest_topup(struct kvm_hyp_memcache *host_mc);
+void hyp_alloc_selftest_reclaim(struct kvm_hyp_memcache *host_mc, unsigned long target);
+#endif
 #endif
diff --git a/arch/arm64/kvm/hyp/nvhe/alloc.c b/arch/arm64/kvm/hyp/nvhe/alloc.c
index 32c923d83f78..49d7560ad150 100644
--- a/arch/arm64/kvm/hyp/nvhe/alloc.c
+++ b/arch/arm64/kvm/hyp/nvhe/alloc.c
@@ -1013,9 +1013,17 @@ int hyp_alloc_errno(void)
 	return hyp_allocator_errno(&hyp_allocator);
 }
 
+static int selftest_init(void);
+
 int hyp_alloc_init(size_t size)
 {
-	return hyp_allocator_init(&hyp_allocator, size);
+	int ret;
+
+	ret = hyp_allocator_init(&hyp_allocator, size);
+	if (ret)
+		return ret;
+
+	return selftest_init();
 }
 
 void hyp_alloc_reclaim(struct kvm_hyp_memcache *mc, unsigned long target)
@@ -1037,3 +1045,179 @@ u32 hyp_alloc_topup_needed(void)
 {
 	return hyp_allocator_topup_needed(&hyp_allocator);
 }
+
+#ifdef CONFIG_NVHE_EL2_DEBUG
+#define SELFTEST_MAX_PAGES 6
+#define SELFTEST_MAX_SIZE (PAGE_SIZE * SELFTEST_MAX_PAGES)
+
+static DEFINE_PER_CPU(int, __selftest_errno);
+static DEFINE_PER_CPU(u32, __selftest_topup_needed);
+
+static struct hyp_allocator selftest_allocator = {
+	.errno = &__selftest_errno,
+	.topup_needed = &__selftest_topup_needed,
+	.lock = __HYP_SPIN_LOCK_UNLOCKED,
+};
+
+int hyp_alloc_selftest_topup(struct kvm_hyp_memcache *host_mc)
+{
+	return hyp_allocator_topup(&selftest_allocator, host_mc);
+}
+
+void hyp_alloc_selftest_reclaim(struct kvm_hyp_memcache *host_mc, unsigned long target)
+{
+	hyp_allocator_reclaim(&selftest_allocator, host_mc, target);
+}
+
+u32 hyp_alloc_selftest_topup_needed(void)
+{
+	return hyp_allocator_topup_needed(&selftest_allocator);
+}
+
+static int selftest_init(void)
+{
+	return hyp_allocator_init(&selftest_allocator, SELFTEST_MAX_SIZE);
+}
+
+static void *selftest_alloc(size_t size)
+{
+	return hyp_allocator_alloc(&selftest_allocator, size);
+}
+
+static void selftest_free(void *addr)
+{
+	hyp_allocator_free(&selftest_allocator, addr);
+}
+
+static int selftest_errno(void)
+{
+	return hyp_allocator_errno(&selftest_allocator);
+}
+
+int hyp_allocator_selftest(void)
+{
+	struct hyp_allocator *allocator = &selftest_allocator;
+	static DEFINE_HYP_SPINLOCK(selftest_lock);
+	struct kvm_hyp_memcache host_mc = { };
+	void *addr1, *addr2, *addr3, *addr4;
+	int ret;
+
+	guard(hyp_spinlock)(&selftest_lock);
+
+	if (allocator->mc.nr_pages < SELFTEST_MAX_PAGES) {
+		*this_cpu_ptr(allocator->topup_needed) = SELFTEST_MAX_PAGES -
+							 allocator->mc.nr_pages;
+		return -ENOMEM;
+	}
+
+	selftest_alloc(SELFTEST_MAX_SIZE);
+	if (selftest_errno() != -E2BIG)
+		return -EINVAL;
+
+	selftest_alloc(SIZE_MAX);
+	if (selftest_errno() != -E2BIG)
+		return -EINVAL;
+
+	/* Test first chunk */
+	addr1 = selftest_alloc(0);
+	if (!addr1 || addr1 != (void *)allocator->start + chunk_hdr_size())
+		return -EINVAL;
+
+	/* Test second contiguous chunk with unaligned size */
+	addr2 = selftest_alloc(MIN_ALLOC_SIZE + 1);
+	if (!addr2)
+		return -EINVAL;
+	addr3 = selftest_alloc(0);
+	if (!addr3 ||
+	    addr3 != addr2 + (2 * MIN_ALLOC_SIZE) + chunk_hdr_size())
+		return -EINVAL;
+
+	selftest_free(addr3);
+
+	/* Test chunk recycling */
+	selftest_free(addr1);
+	if (addr1 != selftest_alloc(0))
+		return -EINVAL;
+
+	/* Test chunk forward merging */
+	addr3 = selftest_alloc(0);
+	selftest_free(addr2);
+	selftest_free(addr1);
+	if (addr1 != selftest_alloc(MIN_ALLOC_SIZE * 2))
+		return -EINVAL;
+
+	selftest_free(addr1);
+
+	/* Test chunk splitting */
+	if (addr1 != selftest_alloc(0))
+		return -EINVAL;
+	if (addr2 != selftest_alloc(0))
+		return -EINVAL;
+
+	/* Test chunk backward merging */
+	selftest_free(addr1);
+	selftest_free(addr2);
+	if (addr1 != selftest_alloc(MIN_ALLOC_SIZE * 2))
+		return -EINVAL;
+
+	selftest_free(addr1);
+
+	/* Test chunk 3-way merging */
+	addr1 = selftest_alloc(0);
+	addr2 = selftest_alloc(0);
+	addr4 = selftest_alloc(0);
+	selftest_free(addr1);
+	selftest_free(addr3);
+	selftest_free(addr2);
+	if (addr1 != selftest_alloc(MIN_ALLOC_SIZE * 3))
+		return -EINVAL;
+
+	selftest_free(addr4);
+	selftest_free(addr1);
+
+	/* Test reclaiming */
+	if (addr1 != selftest_alloc(0))
+		return -EINVAL;
+	if (addr2 != selftest_alloc(PAGE_SIZE * 2))
+		return -EINVAL;
+	addr3 = selftest_alloc(0);
+	addr4 = selftest_alloc(PAGE_SIZE);
+
+	/* Test reclaiming the last chunk of the list */
+	selftest_free(addr4);
+	hyp_allocator_reclaim(allocator, &host_mc, SELFTEST_MAX_PAGES);
+	if (host_mc.nr_pages != SELFTEST_MAX_PAGES - 3)
+		return -EINVAL;
+
+	/* Test punching a hole in the middle of a free chunk ... */
+	selftest_free(addr2);
+	hyp_allocator_reclaim(allocator, &host_mc, SELFTEST_MAX_PAGES);
+	if (host_mc.nr_pages != SELFTEST_MAX_PAGES - 2)
+		return -EINVAL;
+
+	if (selftest_alloc(PAGE_SIZE))
+		return -EINVAL;
+	if (selftest_errno() != -ENOMEM)
+		return -EINVAL;
+
+	/* ... and to refill this hole */
+	ret = hyp_allocator_topup(allocator, &host_mc);
+	if (ret)
+		return ret;
+	/* Chunk at addr2 was made smaller by the reclaim */
+	if (addr2 != selftest_alloc(PAGE_SIZE))
+		return -EINVAL;
+
+	/* Test reclaiming the entire allocator from the host */
+	selftest_free(addr3);
+	selftest_free(addr2);
+	selftest_free(addr1);
+	if (addr1 != selftest_alloc(SELFTEST_MAX_PAGES * PAGE_SIZE - chunk_hdr_size()))
+		return -EINVAL;
+	selftest_free(addr1);
+
+	return 0;
+}
+#else
+static int selftest_init(void) { return 0; }
+#endif
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 346365e76ef2..d99c9b1b0c82 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -633,6 +633,28 @@ static void handle___pkvm_finalize_teardown_vm(struct kvm_cpu_context *host_ctxt
 	cpu_reg(host_ctxt, 1) = __pkvm_finalize_teardown_vm(handle);
 }
 
+#ifdef CONFIG_NVHE_EL2_DEBUG
+static void handle___pkvm_hyp_alloc_selftest(struct kvm_cpu_context *host_ctxt)
+{
+	struct pkvm_hyp_req req = { .type = PKVM_HYP_NO_REQ };
+	int ret;
+
+	ret = hyp_allocator_selftest();
+	if (ret == -ENOMEM) {
+		req.type = PKVM_HYP_REQ_HYP_ALLOC_SELFTEST;
+		req.mem.nr_pages = hyp_alloc_selftest_topup_needed();
+	}
+
+	cpu_reg(host_ctxt, 1) = ret;
+	pkvm_hyp_req_to_smccc(host_ctxt, &req);
+}
+#else
+static void handle___pkvm_hyp_alloc_selftest(struct kvm_cpu_context *host_ctxt)
+{
+	cpu_reg(host_ctxt, 1) = -EPERM;
+}
+#endif
+
 static void handle___pkvm_hyp_topup(struct kvm_cpu_context *host_ctxt)
 {
 	DECLARE_REG(enum pkvm_topup_id, id, host_ctxt, 1);
@@ -648,6 +670,11 @@ static void handle___pkvm_hyp_topup(struct kvm_cpu_context *host_ctxt)
 	case PKVM_TOPUP_HYP_ALLOC:
 		ret = hyp_alloc_topup(&host_mc);
 		break;
+#ifdef CONFIG_NVHE_EL2_DEBUG
+	case PKVM_TOPUP_HYP_ALLOC_SELFTEST:
+		ret = hyp_alloc_selftest_topup(&host_mc);
+		break;
+#endif
 	default:
 		ret = -EINVAL;
 	}
@@ -668,6 +695,11 @@ static void handle___pkvm_hyp_reclaim(struct kvm_cpu_context *host_ctxt)
 	case PKVM_TOPUP_HYP_ALLOC:
 		hyp_alloc_reclaim(&host_mc, target);
 		break;
+#ifdef CONFIG_NVHE_EL2_DEBUG
+	case PKVM_TOPUP_HYP_ALLOC_SELFTEST:
+		hyp_alloc_selftest_reclaim(&host_mc, target);
+		break;
+#endif
 	default:
 		ret = -EINVAL;
 	}
@@ -804,6 +836,7 @@ static const hcall_t host_hcall[] = {
 	HANDLE_FUNC(__pkvm_hyp_topup),
 	HANDLE_FUNC(__pkvm_hyp_reclaim),
 	HANDLE_FUNC(__pkvm_hyp_reclaimable),
+	HANDLE_FUNC(__pkvm_hyp_alloc_selftest),
 
 	HANDLE_FUNC(__pkvm_host_share_hyp),
 	HANDLE_FUNC(__pkvm_host_unshare_hyp),
diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c
index a82e773a1c2d..d28422f5c3d6 100644
--- a/arch/arm64/kvm/pkvm.c
+++ b/arch/arm64/kvm/pkvm.c
@@ -326,6 +326,22 @@ static int __init pkvm_drop_host_privileges(void)
 	return ret;
 }
 
+void __init pkvm_selftests(void)
+{
+#ifdef CONFIG_NVHE_EL2_DEBUG
+	int ret = pkvm_call_hyp_req(__pkvm_hyp_alloc_selftest);
+	unsigned long reclaimed;
+
+	reclaimed = pkvm_hyp_reclaim(PKVM_TOPUP_HYP_ALLOC_SELFTEST, ULONG_MAX);
+
+	/* On failure, not all the pages may be reclaimable */
+	if (!ret)
+		WARN_ON(reclaimed != 6 /* SELFTEST_MAX_PAGES */);
+	else
+		kvm_err("pKVM hyp allocator selftest failed (%d)\n", ret);
+#endif
+}
+
 static int __init finalize_pkvm(void)
 {
 	int ret;
@@ -652,6 +668,9 @@ static int pkvm_handle_hyp_req(struct pkvm_hyp_req *req)
 	case PKVM_HYP_REQ_HYP_ALLOC:
 		ret = pkvm_hyp_topup(PKVM_TOPUP_HYP_ALLOC, req->mem.nr_pages);
 		break;
+	case PKVM_HYP_REQ_HYP_ALLOC_SELFTEST:
+		ret = pkvm_hyp_topup(PKVM_TOPUP_HYP_ALLOC_SELFTEST, req->mem.nr_pages);
+		break;
 	}
 
 	trace_kvm_handle_pkvm_hyp_req(req, ret);
-- 
2.55.0.229.g6434b31f56-goog