KVM: selftests: Read binary stats desc in lib

Move the code to read the binary stats descriptors to the KVM selftests
library. It will be re-used by other tests to check KVM behavior.

No functional change intended.

Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20220613212523.3436117-4-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index f8c104dba258..64ef108cc270 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1850,3 +1850,36 @@ unsigned int vm_calc_num_guest_pages(enum vm_guest_mode mode, size_t size)
 	n = DIV_ROUND_UP(size, vm_guest_mode_params[mode].page_size);
 	return vm_adjust_num_guest_pages(mode, n);
 }
+
+/*
+ * Read binary stats descriptors
+ *
+ * Input Args:
+ *   stats_fd - the file descriptor for the binary stats file from which to read
+ *   header - the binary stats metadata header corresponding to the given FD
+ *
+ * Output Args: None
+ *
+ * Return:
+ *   A pointer to a newly allocated series of stat descriptors.
+ *   Caller is responsible for freeing the returned kvm_stats_desc.
+ *
+ * Read the stats descriptors from the binary stats interface.
+ */
+struct kvm_stats_desc *read_stats_descriptors(int stats_fd,
+					      struct kvm_stats_header *header)
+{
+	struct kvm_stats_desc *stats_desc;
+	ssize_t desc_size, total_size, ret;
+
+	desc_size = get_stats_descriptor_size(header);
+	total_size = header->num_desc * desc_size;
+
+	stats_desc = calloc(header->num_desc, desc_size);
+	TEST_ASSERT(stats_desc, "Allocate memory for stats descriptors");
+
+	ret = pread(stats_fd, stats_desc, total_size, header->desc_offset);
+	TEST_ASSERT(ret == total_size, "Read KVM stats descriptors");
+
+	return stats_desc;
+}