[librm] Add a profiling self-test for measuring mode transition times

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/transitions/librm_test.c

@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/** @file
+ *
+ * Real mode transition self-tests
+ *
+ * This file allows for easy measurement of the time taken to perform
+ * real mode transitions, which may have a substantial overhead when
+ * running under a hypervisor.
+ *
+ */
+
+/* Forcibly enable assertions */
+#undef NDEBUG
+
+#include <ipxe/test.h>
+#include <ipxe/profile.h>
+#include <realmode.h>
+
+/** Number of sample iterations for profiling */
+#define PROFILE_COUNT 4096
+
+/** Protected-to-real mode transition profiler */
+static struct profiler p2r_profiler __profiler = { .name = "p2r" };
+
+/** Real-to-protected mode transition profiler */
+static struct profiler r2p_profiler __profiler = { .name = "r2p" };
+
+/**
+ * Perform real mode transition self-tests
+ *
+ */
+static void librm_test_exec ( void ) {
+	unsigned int i;
+	unsigned long p2r_elapsed;
+
+	/* Profile mode transitions.  We want to profile each
+	 * direction of the transition separately, so perform an RDTSC
+	 * while in real mode and tweak the profilers' start/stop
+	 * times appropriately.
+	 */
+	for ( i = 0 ; i < PROFILE_COUNT ; i++ ) {
+		profile_start ( &p2r_profiler );
+		__asm__ __volatile__ ( REAL_CODE ( "rdtsc\n\t" )
+				       : "=A" ( r2p_profiler.started ) : );
+		profile_stop ( &r2p_profiler );
+		p2r_elapsed = ( r2p_profiler.started - p2r_profiler.started );
+		profile_update ( &p2r_profiler, p2r_elapsed );
+	}
+}
+
+/** Real mode transition self-test */
+struct self_test librm_test __self_test = {
+	.name = "librm",
+	.exec = librm_test_exec,
+};
+
+REQUIRE_OBJECT ( test );