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Date:   Wed, 13 Apr 2022 10:59:39 -0700
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Subject: [PATCH v5 05/10] KVM: selftests: Read binary stat data in lib
From:   Ben Gardon <bgardon@google.com>
To:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc:     Paolo Bonzini <pbonzini@redhat.com>, Peter Xu <peterx@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        David Matlack <dmatlack@google.com>,
        Jim Mattson <jmattson@google.com>,
        David Dunn <daviddunn@google.com>,
        Jing Zhang <jingzhangos@google.com>,
        Junaid Shahid <junaids@google.com>,
        Ben Gardon <bgardon@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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

No functional change intended.

Signed-off-by: Ben Gardon <bgardon@google.com>
---
 .../selftests/kvm/include/kvm_util_base.h     |  3 ++
 .../selftests/kvm/kvm_binary_stats_test.c     |  7 ++--
 tools/testing/selftests/kvm/lib/kvm_util.c    | 36 +++++++++++++++++++
 3 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index fabe46ddc1b2..2a3a4d9ed8e3 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -403,6 +403,9 @@ int vcpu_get_stats_fd(struct kvm_vm *vm, uint32_t vcpuid);
 void read_stats_header(int stats_fd, struct kvm_stats_header *header);
 struct kvm_stats_desc *read_stats_desc(int stats_fd,
 				       struct kvm_stats_header *header);
+int read_stat_data(int stats_fd, struct kvm_stats_header *header,
+		   struct kvm_stats_desc *desc, uint64_t *data,
+		   ssize_t max_elements);
 
 uint32_t guest_get_vcpuid(void);
 
diff --git a/tools/testing/selftests/kvm/kvm_binary_stats_test.c b/tools/testing/selftests/kvm/kvm_binary_stats_test.c
index 8b31f8fc7e08..59677fae26e5 100644
--- a/tools/testing/selftests/kvm/kvm_binary_stats_test.c
+++ b/tools/testing/selftests/kvm/kvm_binary_stats_test.c
@@ -160,11 +160,8 @@ static void stats_test(int stats_fd)
 	size_data = 0;
 	for (i = 0; i < header.num_desc; ++i) {
 		pdesc = (void *)stats_desc + i * size_desc;
-		ret = pread(stats_fd, stats_data,
-				pdesc->size * sizeof(*stats_data),
-				header.data_offset + size_data);
-		TEST_ASSERT(ret == pdesc->size * sizeof(*stats_data),
-				"Read data of KVM stats: %s", pdesc->name);
+		read_stat_data(stats_fd, &header, pdesc, stats_data,
+			       pdesc->size);
 		size_data += pdesc->size * sizeof(*stats_data);
 	}
 
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 12fa8cc88043..fc2321055a69 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -2615,3 +2615,39 @@ struct kvm_stats_desc *read_stats_desc(int stats_fd,
 
 	return stats_desc;
 }
+
+/*
+ * Read stat data for a particular stat
+ *
+ * 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
+ *   desc - the binary stat metadata for the particular stat to be read
+ *   max_elements - the maximum number of 8-byte values to read into data
+ *
+ * Output Args:
+ *   data - the buffer into which stat data should be read
+ *
+ * Return:
+ *   The number of data elements read into data or -ERRNO on error.
+ *
+ * Read the data values of a specified stat from the binary stats interface.
+ */
+int read_stat_data(int stats_fd, struct kvm_stats_header *header,
+		   struct kvm_stats_desc *desc, uint64_t *data,
+		   ssize_t max_elements)
+{
+	ssize_t size = min((ssize_t)desc->size, max_elements);
+	ssize_t ret;
+
+	ret = pread(stats_fd, data, size * sizeof(*data),
+		    header->data_offset + desc->offset);
+
+	/* ret from pread is in bytes. */
+	ret = ret / sizeof(*data);
+
+	TEST_ASSERT(ret == size,
+		    "Read data of KVM stats: %s", desc->name);
+
+	return ret;
+}
-- 
2.35.1.1178.g4f1659d476-goog