[PATCH v2 2/3] KVM: selftests: arm64: Skip sea_to_user without 1GB hugepages

[Like Xu <like.xu.linux@gmail.com>]

sea_to_user backs guest memory with 1GB hugepages but never checks that
any are reserved. On a host with an empty pool it aborts instead of
skipping:

  kvm_syscalls.h:68: mem != MAP_FAILED, errno=12 (ENOMEM)
  not ok 1 selftests: kvm: sea_to_user # exit=254

The mmap() of the hugetlb region fails with -ENOMEM because no 1GB pages
are available, and the test treats that as a hard failure even though it
simply cannot run without the backing pages. Check the free 1GB hugepage
count up front and skip cleanly when the host cannot satisfy the region.

Signed-off-by: Like Xu <likexu@tencent.com>
---
 tools/testing/selftests/kvm/arm64/sea_to_user.c |  6 ++++++
 tools/testing/selftests/kvm/include/test_util.h |  1 +
 tools/testing/selftests/kvm/lib/test_util.c     | 15 +++++++++++++++
 3 files changed, 22 insertions(+)

diff --git a/tools/testing/selftests/kvm/arm64/sea_to_user.c b/tools/testing/selftests/kvm/arm64/sea_to_user.c
index 1c2a743ca8e23..7cf95da8e594d 100644
--- a/tools/testing/selftests/kvm/arm64/sea_to_user.c
+++ b/tools/testing/selftests/kvm/arm64/sea_to_user.c
@@ -281,6 +281,12 @@ static struct kvm_vm *vm_create_with_sea_handler(struct kvm_vcpu **vcpu)
 	alignment = max(backing_page_size, guest_page_size);
 	num_guest_pages = VM_MEM_SIZE / guest_page_size;
 
+	/*
+	 * The region is backed by 1GB hugepages; skip gracefully rather than
+	 * failing with mmap() -ENOMEM if the host has none reserved.
+	 */
+	TEST_REQUIRE(get_free_hugepages(backing_page_size) >= VM_MEM_SIZE);
+
 	vm = __vm_create_with_one_vcpu(vcpu, num_guest_pages, guest_code);
 	vm_init_descriptor_tables(vm);
 	vcpu_init_descriptor_tables(*vcpu);
diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index a56271c237ae9..0624922c2735d 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -168,6 +168,7 @@ struct vm_mem_backing_src_alias {
 bool thp_configured(void);
 size_t get_trans_hugepagesz(void);
 size_t get_def_hugetlb_pagesz(void);
+size_t get_free_hugepages(size_t page_size);
 const struct vm_mem_backing_src_alias *vm_mem_backing_src_alias(u32 i);
 size_t get_backing_src_pagesz(u32 i);
 bool is_backing_src_hugetlb(u32 i);
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index bab1bd2b775b6..29f9c1d60b1b7 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -222,6 +222,21 @@ size_t get_def_hugetlb_pagesz(void)
 	TEST_FAIL("Error in reading /proc/meminfo");
 }
 
+size_t get_free_hugepages(size_t page_size)
+{
+	char path[128];
+	size_t free;
+
+	snprintf(path, sizeof(path),
+		 "/sys/kernel/mm/hugepages/hugepages-%zukB/free_hugepages",
+		 page_size >> 10);
+	if (!test_sysfs_path(path))
+		return 0;
+
+	free = get_sysfs_val(path);
+	return free * page_size;
+}
+
 #define ANON_FLAGS	(MAP_PRIVATE | MAP_ANONYMOUS)
 #define ANON_HUGE_FLAGS	(ANON_FLAGS | MAP_HUGETLB)
 
-- 
2.50.1 (Apple Git-155)