KVM: selftests: Don't require THP to run tests

Unless we want to test with THP, then we shouldn't require it to be
configured by the host kernel. Unfortunately, even advising with
MADV_NOHUGEPAGE does require it, so check for THP first in order
to avoid madvise failing with EINVAL.
Signed-off-by: Andrew Jones <drjones@redhat.com>
Message-Id: <20201029201703.102716-2-drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/lib/kvm_util.c

@@ -14,6 +14,7 @@
 #include <sys/mman.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <unistd.h>
 #include <linux/kernel.h>
 
 #define KVM_UTIL_PGS_PER_HUGEPG 512
@@ -664,14 +665,22 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
 
 	/* As needed perform madvise */
 	if (src_type == VM_MEM_SRC_ANONYMOUS || src_type == VM_MEM_SRC_ANONYMOUS_THP) {
+		struct stat statbuf;
+
+		ret = stat("/sys/kernel/mm/transparent_hugepage", &statbuf);
+		TEST_ASSERT(ret == 0 || (ret == -1 && errno == ENOENT),
+			    "stat /sys/kernel/mm/transparent_hugepage");
+
+		TEST_ASSERT(ret == 0 || src_type != VM_MEM_SRC_ANONYMOUS_THP,
+			    "VM_MEM_SRC_ANONYMOUS_THP requires THP to be configured in the host kernel");
+
+		if (ret == 0) {
 			ret = madvise(region->host_mem, npages * vm->page_size,
 				      src_type == VM_MEM_SRC_ANONYMOUS ? MADV_NOHUGEPAGE : MADV_HUGEPAGE);
-		TEST_ASSERT(ret == 0, "madvise failed,\n"
-			    "  addr: %p\n"
-			    "  length: 0x%lx\n"
-			    "  src_type: %x",
+			TEST_ASSERT(ret == 0, "madvise failed, addr: %p length: 0x%lx src_type: %x",
 				    region->host_mem, npages * vm->page_size, src_type);
 		}
+	}
 
 	region->unused_phy_pages = sparsebit_alloc();
 	sparsebit_set_num(region->unused_phy_pages,