[RFC PATCH v2 2/2] KVM: selftests: update guest_memfd write tests

[Nikita Kalyazin <kalyazin@amazon.com>]

This is to reflect that the write syscall is now implemented for
guest_memfd.

Signed-off-by: Nikita Kalyazin <kalyazin@amazon.com>
---
 .../testing/selftests/kvm/guest_memfd_test.c  | 85 +++++++++++++++++--
 1 file changed, 79 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index ce687f8d248f..e10d0f51da93 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -20,18 +20,90 @@
 #include "kvm_util.h"
 #include "test_util.h"
 
-static void test_file_read_write(int fd)
+static void test_file_read(int fd)
 {
 	char buf[64];
 
 	TEST_ASSERT(read(fd, buf, sizeof(buf)) < 0,
 		    "read on a guest_mem fd should fail");
-	TEST_ASSERT(write(fd, buf, sizeof(buf)) < 0,
-		    "write on a guest_mem fd should fail");
 	TEST_ASSERT(pread(fd, buf, sizeof(buf), 0) < 0,
 		    "pread on a guest_mem fd should fail");
-	TEST_ASSERT(pwrite(fd, buf, sizeof(buf), 0) < 0,
-		    "pwrite on a guest_mem fd should fail");
+}
+
+static void test_file_write(int fd, size_t total_size)
+{
+	size_t page_size = getpagesize();
+	void *buf = NULL;
+	int ret;
+
+	ret = posix_memalign(&buf, page_size, total_size);
+	TEST_ASSERT_EQ(ret, 0);
+
+	/* Check arguments correctness checks work as expected */
+
+	ret = pwrite(fd, buf, page_size - 1, 0);
+	TEST_ASSERT(ret == -1, "write unaligned count on a guest_mem fd should fail");
+	TEST_ASSERT_EQ(errno, EINVAL);
+
+	ret = pwrite(fd, buf, page_size, 1);
+	TEST_ASSERT(ret == -1, "write unaligned offset on a guest_mem fd should fail");
+	TEST_ASSERT_EQ(errno, EINVAL);
+
+	ret = pwrite(fd, buf, page_size, total_size);
+	TEST_ASSERT(ret == -1, "writing past the file size on a guest_mem fd should fail");
+	TEST_ASSERT_EQ(errno, EINVAL);
+
+	ret = pwrite(fd, NULL, page_size, 0);
+	TEST_ASSERT(ret == -1, "supplying a NULL buffer when writing a guest_mem fd should fail");
+	TEST_ASSERT_EQ(errno, EINVAL);
+
+	/* Check double population is not allowed */
+
+	ret = pwrite(fd, buf, page_size, 0);
+	TEST_ASSERT(ret == page_size, "page-aligned write on a guest_mem fd should succeed");
+
+	ret = pwrite(fd, buf, page_size, 0);
+	TEST_ASSERT(ret == -1, "write on already populated guest_mem fd should fail");
+	TEST_ASSERT_EQ(errno, ENOSPC);
+
+	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page_size);
+	TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) should succeed");
+
+	/* Check population is allowed again after punching a hole */
+
+	ret = pwrite(fd, buf, page_size, 0);
+	TEST_ASSERT(ret == page_size, "page-aligned write on a punched guest_mem fd should succeed");
+
+	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page_size);
+	TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) should succeed");
+
+	/* Check population of already allocated memory is allowed */
+
+	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, page_size);
+	TEST_ASSERT(!ret, "fallocate with aligned offset and size should succeed");
+
+	ret = pwrite(fd, buf, page_size, 0);
+	TEST_ASSERT(ret == page_size, "write on a preallocated guest_mem fd should succeed");
+
+	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page_size);
+	TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) should succeed");
+
+	/* Check population works until an already populated page is encountered */
+
+	ret = pwrite(fd, buf, total_size, 0);
+	TEST_ASSERT(ret == total_size, "page-aligned write on a guest_mem fd should succeed");
+
+	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, page_size);
+	TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) should succeed");
+
+	ret = pwrite(fd, buf, total_size, 0);
+	TEST_ASSERT(ret == page_size, "write on a guest_mem fd should not overwrite data");
+
+	ret = fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, total_size);
+	TEST_ASSERT(!ret, "fallocate(PUNCH_HOLE) should succeed");
+
+
+	free(buf);
 }
 
 static void test_mmap(int fd, size_t page_size)
@@ -189,7 +261,8 @@ int main(int argc, char *argv[])
 
 	fd = vm_create_guest_memfd(vm, total_size, 0);
 
-	test_file_read_write(fd);
+	test_file_read(fd);
+	test_file_write(fd, total_size);
 	test_mmap(fd, page_size);
 	test_file_size(fd, page_size, total_size);
 	test_fallocate(fd, page_size, total_size);
-- 
2.40.1