[kvm-unit-tests PATCH v2 1/1] s390x: add parallel skey migration test

[Nico Boehr <nrb@linux.ibm.com>]

Right now, we have a test which sets storage keys, then migrates the VM
and - after migration finished - verifies the skeys are still there.

Add a new version of the test which changes storage keys while the
migration is in progress. This is achieved by adding a command line
argument to the existing migration-skey test.

Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
---
 s390x/migration-skey.c | 214 +++++++++++++++++++++++++++++++++++------
 s390x/unittests.cfg    |  15 ++-
 2 files changed, 198 insertions(+), 31 deletions(-)

diff --git a/s390x/migration-skey.c b/s390x/migration-skey.c
index b7bd82581abe..9b9a45f4ad3b 100644
--- a/s390x/migration-skey.c
+++ b/s390x/migration-skey.c
@@ -2,6 +2,12 @@
 /*
  * Storage Key migration tests
  *
+ * There are two variants of this test:
+ * - sequential: sets some storage keys on pages, migrates the VM and then
+ *   verifies the storage keys are still as we expect.
+ * - parallel: start migration of a VM and set and check storage keys on some
+ *   pages while migration is in process.
+ *
  * Copyright IBM Corp. 2022
  *
  * Authors:
@@ -10,20 +16,44 @@
 
 #include <libcflat.h>
 #include <asm/facility.h>
-#include <asm/page.h>
 #include <asm/mem.h>
-#include <asm/interrupt.h>
+#include <asm/page.h>
+#include <asm/barrier.h>
 #include <hardware.h>
+#include <smp.h>
+
+struct skey_verify_result {
+	bool verify_failed;
+	union skey expected_key;
+	union skey actual_key;
+	unsigned long page_mismatch_idx;
+	unsigned long page_mismatch_addr;
+};
 
 #define NUM_PAGES 128
-static uint8_t pagebuf[NUM_PAGES][PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
+static uint8_t pagebuf[NUM_PAGES * PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
+
+static struct skey_verify_result result;
 
-static void test_migration(void)
+static unsigned int thread_iters;
+static bool thread_should_exit;
+static bool thread_exited;
+
+/*
+ * Set storage key test pattern on pagebuf with a seed for the storage keys.
+ *
+ * Each page's storage key is generated by taking the page's index in pagebuf,
+ * XOR-ing that with the given seed and then multipling the result with two.
+ *
+ * pagebuf must point to page_count consecutive pages.
+ * Only the lower seven bits of the seed are considered.
+ */
+static void skey_set_test_pattern(uint8_t *pagebuf, unsigned long page_count, unsigned char seed)
 {
-	union skey expected_key, actual_key;
-	int i, key_to_set, key_mismatches = 0;
+	unsigned char key_to_set;
+	unsigned long i;
 
-	for (i = 0; i < NUM_PAGES; i++) {
+	for (i = 0; i < page_count; i++) {
 		/*
 		 * Storage keys are 7 bit, lowest bit is always returned as zero
 		 * by iske.
@@ -31,16 +61,34 @@ static void test_migration(void)
 		 * protection as well as reference and change indication for
 		 * some keys.
 		 */
-		key_to_set = i * 2;
-		set_storage_key(pagebuf[i], key_to_set, 1);
+		key_to_set = (i ^ seed) * 2;
+		set_storage_key(pagebuf + i * PAGE_SIZE, key_to_set, 1);
 	}
+}
 
-	puts("Please migrate me, then press return\n");
-	(void)getchar();
+/*
+ * Verify storage keys on pagebuf.
+ * Storage keys must have been set by skey_set_test_pattern on pagebuf before.
+ * skey_set_keys must have been called with the same seed value.
+ *
+ * If storage keys match the expected result, will return a skey_verify_result
+ * with verify_failed false. All other fields are then invalid.
+ * If there is a mismatch, returned struct will have verify_failed true and will
+ * be filled with the details on the first mismatch encountered.
+ */
+static struct skey_verify_result skey_verify_test_pattern(uint8_t *pagebuf, unsigned long page_count, unsigned char seed)
+{
+	union skey expected_key, actual_key;
+	struct skey_verify_result result = {
+		.verify_failed = true
+	};
+	uint8_t *cur_page;
+	unsigned long i;
 
-	for (i = 0; i < NUM_PAGES; i++) {
-		actual_key.val = get_storage_key(pagebuf[i]);
-		expected_key.val = i * 2;
+	for (i = 0; i < page_count; i++) {
+		cur_page = pagebuf + i * PAGE_SIZE;
+		actual_key.val = get_storage_key(cur_page);
+		expected_key.val = (i ^ seed) * 2;
 
 		/*
 		 * The PoP neither gives a guarantee that the reference bit is
@@ -51,33 +99,145 @@ static void test_migration(void)
 		actual_key.str.rf = 0;
 		expected_key.str.rf = 0;
 
-		/* don't log anything when key matches to avoid spamming the log */
 		if (actual_key.val != expected_key.val) {
-			key_mismatches++;
-			report_fail("page %d expected_key=0x%x actual_key=0x%x", i, expected_key.val, actual_key.val);
+			result.expected_key.val = expected_key.val;
+			result.actual_key.val = actual_key.val;
+			result.page_mismatch_idx = i;
+			result.page_mismatch_addr = (unsigned long)cur_page;
+			return result;
 		}
 	}
 
-	report(!key_mismatches, "skeys after migration match");
+	result.verify_failed = false;
+	return result;
+}
+
+static void skey_report_verify(struct skey_verify_result * const result)
+{
+	if (result->verify_failed)
+		report_fail("page skey mismatch: first page idx = %lu, addr = 0x%lx, "
+			"expected_key = 0x%x, actual_key = 0x%x",
+			result->page_mismatch_idx, result->page_mismatch_addr,
+			result->expected_key.val, result->actual_key.val);
+	else
+		report_pass("skeys match");
+}
+
+static void migrate_once(void)
+{
+	static bool migrated;
+
+	if (migrated)
+		return;
+
+	migrated = true;
+	puts("Please migrate me, then press return\n");
+	(void)getchar();
 }
 
-int main(void)
+static void test_skey_migration_sequential(void)
+{
+	report_prefix_push("sequential");
+
+	skey_set_test_pattern(pagebuf, NUM_PAGES, 0);
+
+	migrate_once();
+
+	result = skey_verify_test_pattern(pagebuf, NUM_PAGES, 0);
+	skey_report_verify(&result);
+
+	report_prefix_pop();
+}
+
+static void set_skeys_thread(void)
+{
+	while (!READ_ONCE(thread_should_exit)) {
+		skey_set_test_pattern(pagebuf, NUM_PAGES, thread_iters);
+
+		result = skey_verify_test_pattern(pagebuf, NUM_PAGES, thread_iters);
+
+		/*
+		 * Always increment even if the verify fails. This ensures primary CPU knows where
+		 * we left off and can do an additional verify round after migration finished.
+		 */
+		thread_iters++;
+
+		if (result.verify_failed)
+			break;
+	}
+
+	WRITE_ONCE(thread_exited, 1);
+}
+
+static void test_skey_migration_parallel(void)
+{
+	report_prefix_push("parallel");
+
+	if (smp_query_num_cpus() == 1) {
+		report_skip("need at least 2 cpus for this test");
+		goto error;
+	}
+
+	smp_cpu_setup(1, PSW_WITH_CUR_MASK(set_skeys_thread));
+
+	migrate_once();
+
+	WRITE_ONCE(thread_should_exit, 1);
+
+	while (!thread_exited)
+		mb();
+
+	report_info("thread completed %u iterations", thread_iters);
+
+	report_prefix_push("during migration");
+	skey_report_verify(&result);
+	report_prefix_pop();
+
+	/*
+	 * Verification of skeys occurs on the thread. We don't know if we
+	 * were still migrating during the verification.
+	 * To be sure, make another verification round after the migration
+	 * finished to catch skeys which might not have been migrated
+	 * correctly.
+	 */
+	report_prefix_push("after migration");
+	assert(thread_iters > 0);
+	result = skey_verify_test_pattern(pagebuf, NUM_PAGES, thread_iters - 1);
+	skey_report_verify(&result);
+	report_prefix_pop();
+
+error:
+	report_prefix_pop();
+}
+
+static void print_usage(void)
+{
+	report_info("Usage: migration-skey [parallel|sequential]");
+}
+
+int main(int argc, char **argv)
 {
 	report_prefix_push("migration-skey");
 	if (test_facility(169)) {
 		report_skip("storage key removal facility is active");
+		goto error;
+	}
 
-		/*
-		 * If we just exit and don't ask migrate_cmd to migrate us, it
-		 * will just hang forever. Hence, also ask for migration when we
-		 * skip this test altogether.
-		 */
-		puts("Please migrate me, then press return\n");
-		(void)getchar();
+	if (argc < 2) {
+		print_usage();
+		goto error;
+	}
+
+	if (!strcmp("parallel", argv[1])) {
+		test_skey_migration_parallel();
+	} else if (!strcmp("sequential", argv[1])) {
+		test_skey_migration_sequential();
 	} else {
-		test_migration();
+		print_usage();
 	}
 
+error:
+	migrate_once();
 	report_prefix_pop();
 	return report_summary();
 }
diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
index 3caf81eda396..7763cb857954 100644
--- a/s390x/unittests.cfg
+++ b/s390x/unittests.cfg
@@ -185,10 +185,6 @@ smp = 2
 file = migration-cmm.elf
 groups = migration
 
-[migration-skey]
-file = migration-skey.elf
-groups = migration
-
 [panic-loop-extint]
 file = panic-loop-extint.elf
 groups = panic
@@ -208,3 +204,14 @@ groups = migration
 [exittime]
 file = exittime.elf
 smp = 2
+
+[migration-skey-sequential]
+file = migration-skey.elf
+groups = migration
+extra_params = -append 'sequential'
+
+[migration-skey-parallel]
+file = migration-skey.elf
+smp = 2
+groups = migration
+extra_params = -append 'parallel'
-- 
2.36.1