[kvm-unit-tests PATCH v1 0/2] s390x: test CMM during migration

[kvm-unit-tests PATCH v1 0/2] s390x: test CMM during migration

[Nico Boehr]

Add a test which changes CMM page states while VM is being migrated.

Nico Boehr (2):
  s390x: add a library for CMM-related functions
  s390x: add CMM test during migration

 lib/s390x/cmm.c              |  83 ++++++++++++++++++++++++++
 lib/s390x/cmm.h              |  29 +++++++++
 s390x/Makefile               |   2 +
 s390x/migration-cmm.c        |  36 ++++--------
 s390x/migration-during-cmm.c | 111 +++++++++++++++++++++++++++++++++++
 s390x/unittests.cfg          |   5 ++
 6 files changed, 240 insertions(+), 26 deletions(-)
 create mode 100644 lib/s390x/cmm.c
 create mode 100644 lib/s390x/cmm.h
 create mode 100644 s390x/migration-during-cmm.c

-- 
2.36.1

[kvm-unit-tests PATCH v1 1/2] s390x: add a library for CMM-related functions

[Nico Boehr]

Upcoming changes will add a test which is very similar to the existing
CMM migration test. To reduce code duplication, move the common function
to a library which can be re-used by both tests.

Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
---
 lib/s390x/cmm.c       | 83 +++++++++++++++++++++++++++++++++++++++++++
 lib/s390x/cmm.h       | 29 +++++++++++++++
 s390x/Makefile        |  1 +
 s390x/migration-cmm.c | 36 ++++++-------------
 4 files changed, 123 insertions(+), 26 deletions(-)
 create mode 100644 lib/s390x/cmm.c
 create mode 100644 lib/s390x/cmm.h

diff --git a/lib/s390x/cmm.c b/lib/s390x/cmm.c
new file mode 100644
index 000000000000..9609cea68950
--- /dev/null
+++ b/lib/s390x/cmm.c
@@ -0,0 +1,83 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * CMM test library
+ *
+ * Copyright IBM Corp. 2022
+ *
+ * Authors:
+ *  Nico Boehr <nrb@linux.ibm.com>
+ */
+#include <libcflat.h>
+#include <bitops.h>
+#include "cmm.h"
+
+/*
+ * Maps ESSA actions to states the page is allowed to be in after the
+ * respective action was executed.
+ */
+const int allowed_essa_state_masks[4] = {
+	BIT(ESSA_USAGE_STABLE),					/* ESSA_SET_STABLE */
+	BIT(ESSA_USAGE_UNUSED),					/* ESSA_SET_UNUSED */
+	BIT(ESSA_USAGE_VOLATILE),				/* ESSA_SET_VOLATILE */
+	BIT(ESSA_USAGE_VOLATILE) | BIT(ESSA_USAGE_POT_VOLATILE) /* ESSA_SET_POT_VOLATILE */
+};
+
+static inline unsigned long get_page_addr(uint8_t *pagebuf, int page_idx)
+{
+	return (unsigned long)(pagebuf + PAGE_SIZE * page_idx);
+}
+
+/*
+ * Set CMM page states on pagebuf.
+ * pagebuf must point to page_count consecutive pages.
+ * page_count must be a multiple of 4.
+ */
+void cmm_set_page_states(uint8_t *pagebuf, int page_count)
+{
+	int i;
+
+	assert(page_count % 4 == 0);
+	for (i = 0; i < page_count; i += 4) {
+		essa(ESSA_SET_STABLE, get_page_addr(pagebuf, i));
+		essa(ESSA_SET_UNUSED, get_page_addr(pagebuf, i + 1));
+		essa(ESSA_SET_VOLATILE, get_page_addr(pagebuf, i + 2));
+		essa(ESSA_SET_POT_VOLATILE, get_page_addr(pagebuf, i + 3));
+	}
+}
+
+/*
+ * Verify CMM page states on pagebuf.
+ * Page states must have been set by cmm_set_page_states on pagebuf before.
+ * page_count must be a multiple of 4.
+ *
+ * If page states match the expected result,
+ * will return true and result will be untouched. When a mismatch occurs, will
+ * return false and result will be filled with details on the first mismatch.
+ */
+bool cmm_verify_page_states(uint8_t *pagebuf, int page_count, struct cmm_verify_result *result)
+{
+	int i, state_mask, actual_state;
+
+	assert(page_count % 4 == 0);
+
+	for (i = 0; i < page_count; i++) {
+		actual_state = essa(ESSA_GET_STATE, get_page_addr(pagebuf, i));
+		/* extract the usage state in bits 60 and 61 */
+		actual_state = (actual_state >> 2) & 0x3;
+		state_mask = allowed_essa_state_masks[i % ARRAY_SIZE(allowed_essa_state_masks)];
+		if (!(BIT(actual_state) & state_mask)) {
+			result->page_mismatch = i;
+			result->expected_mask = state_mask;
+			result->actual_mask = BIT(actual_state);
+			return false;
+		}
+	}
+
+	return true;
+}
+
+void cmm_report_verify_fail(struct cmm_verify_result const *result)
+{
+	report_fail("page state mismatch: first page = %d, expected_mask = 0x%x, actual_mask = 0x%x", result->page_mismatch, result->expected_mask, result->actual_mask);
+}
+
diff --git a/lib/s390x/cmm.h b/lib/s390x/cmm.h
new file mode 100644
index 000000000000..56e188c78704
--- /dev/null
+++ b/lib/s390x/cmm.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * CMM test library
+ *
+ * Copyright IBM Corp. 2022
+ *
+ * Authors:
+ *  Nico Boehr <nrb@linux.ibm.com>
+ */
+#ifndef S390X_CMM_H
+#define S390X_CMM_H
+
+#include <libcflat.h>
+#include <asm/page.h>
+#include <asm/cmm.h>
+
+struct cmm_verify_result {
+	int page_mismatch;
+	int expected_mask;
+	int actual_mask;
+};
+
+void cmm_set_page_states(uint8_t *pagebuf, int page_count);
+
+bool cmm_verify_page_states(uint8_t *pagebuf, int page_count, struct cmm_verify_result *result);
+
+void cmm_report_verify_fail(struct cmm_verify_result const *result);
+
+#endif /* S390X_CMM_H */
diff --git a/s390x/Makefile b/s390x/Makefile
index bf1504f9d58c..401cb6371cee 100644
--- a/s390x/Makefile
+++ b/s390x/Makefile
@@ -99,6 +99,7 @@ cflatobjs += lib/s390x/malloc_io.o
 cflatobjs += lib/s390x/uv.o
 cflatobjs += lib/s390x/sie.o
 cflatobjs += lib/s390x/fault.o
+cflatobjs += lib/s390x/cmm.o
 
 OBJDIRS += lib/s390x
 
diff --git a/s390x/migration-cmm.c b/s390x/migration-cmm.c
index aa7910ca76bf..ffd656f4db75 100644
--- a/s390x/migration-cmm.c
+++ b/s390x/migration-cmm.c
@@ -14,41 +14,25 @@
 #include <asm/cmm.h>
 #include <bitops.h>
 
+#include "cmm.h"
+
 #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 void test_migration(void)
 {
-	int i, state_mask, actual_state;
-	/*
-	 * Maps ESSA actions to states the page is allowed to be in after the
-	 * respective action was executed.
-	 */
-	int allowed_essa_state_masks[4] = {
-		BIT(ESSA_USAGE_STABLE),					/* ESSA_SET_STABLE */
-		BIT(ESSA_USAGE_UNUSED),					/* ESSA_SET_UNUSED */
-		BIT(ESSA_USAGE_VOLATILE),				/* ESSA_SET_VOLATILE */
-		BIT(ESSA_USAGE_VOLATILE) | BIT(ESSA_USAGE_POT_VOLATILE) /* ESSA_SET_POT_VOLATILE */
-	};
+	struct cmm_verify_result result = {};
 
-	assert(NUM_PAGES % 4 == 0);
-	for (i = 0; i < NUM_PAGES; i += 4) {
-		essa(ESSA_SET_STABLE, (unsigned long)pagebuf[i]);
-		essa(ESSA_SET_UNUSED, (unsigned long)pagebuf[i + 1]);
-		essa(ESSA_SET_VOLATILE, (unsigned long)pagebuf[i + 2]);
-		essa(ESSA_SET_POT_VOLATILE, (unsigned long)pagebuf[i + 3]);
-	}
+	cmm_set_page_states(pagebuf, NUM_PAGES);
 
 	puts("Please migrate me, then press return\n");
 	(void)getchar();
 
-	for (i = 0; i < NUM_PAGES; i++) {
-		actual_state = essa(ESSA_GET_STATE, (unsigned long)pagebuf[i]);
-		/* extract the usage state in bits 60 and 61 */
-		actual_state = (actual_state >> 2) & 0x3;
-		state_mask = allowed_essa_state_masks[i % ARRAY_SIZE(allowed_essa_state_masks)];
-		report(BIT(actual_state) & state_mask, "page %d state: expected_mask=0x%x actual_mask=0x%lx", i, state_mask, BIT(actual_state));
-	}
+	if (!cmm_verify_page_states(pagebuf, NUM_PAGES, &result))
+		cmm_report_verify_fail(&result);
+	else
+		report_pass("page states match");
 }
 
 int main(void)
-- 
2.36.1

[kvm-unit-tests PATCH v1 2/2] s390x: add CMM test during migration

[Nico Boehr]

Add a test which modifies CMM page states while migration is in
progress.

Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
---
 s390x/Makefile               |   1 +
 s390x/migration-during-cmm.c | 111 +++++++++++++++++++++++++++++++++++
 s390x/unittests.cfg          |   5 ++
 3 files changed, 117 insertions(+)
 create mode 100644 s390x/migration-during-cmm.c

diff --git a/s390x/Makefile b/s390x/Makefile
index 401cb6371cee..64c7c04409ae 100644
--- a/s390x/Makefile
+++ b/s390x/Makefile
@@ -39,6 +39,7 @@ tests += $(TEST_DIR)/panic-loop-extint.elf
 tests += $(TEST_DIR)/panic-loop-pgm.elf
 tests += $(TEST_DIR)/migration-sck.elf
 tests += $(TEST_DIR)/exittime.elf
+tests += $(TEST_DIR)/migration-during-cmm.elf
 
 pv-tests += $(TEST_DIR)/pv-diags.elf
 
diff --git a/s390x/migration-during-cmm.c b/s390x/migration-during-cmm.c
new file mode 100644
index 000000000000..3c96283d7b00
--- /dev/null
+++ b/s390x/migration-during-cmm.c
@@ -0,0 +1,111 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Perform CMMA actions while migrating.
+ *
+ * Copyright IBM Corp. 2022
+ *
+ * Authors:
+ *  Nico Boehr <nrb@linux.ibm.com>
+ */
+
+#include <libcflat.h>
+#include <smp.h>
+#include <asm-generic/barrier.h>
+
+#include "cmm.h"
+
+#define NUM_PAGES 128
+
+static uint8_t pagebuf[NUM_PAGES * PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
+
+static int thread_iters;
+static int thread_should_exit;
+static int thread_exited;
+static bool verification_failure_occured;
+struct cmm_verify_result result;
+
+static void test_cmm_during_migration(void)
+{
+	/*
+	 * The second CPU must not print on the console, otherwise it will race with
+	 * the primary CPU on the SCLP buffer.
+	 */
+	while (!thread_should_exit) {
+		cmm_set_page_states(pagebuf, NUM_PAGES);
+		if (!cmm_verify_page_states(pagebuf, NUM_PAGES, &result)) {
+			verification_failure_occured = true;
+			goto out;
+		}
+		thread_iters++;
+	}
+
+out:
+	thread_exited = 1;
+}
+
+int main(void)
+{
+	bool has_essa = check_essa_available();
+	struct psw psw;
+
+	report_prefix_push("migration-during-cmm");
+	if (!has_essa) {
+		report_skip("ESSA is not available");
+		goto error;
+	}
+
+	if (smp_query_num_cpus() == 1) {
+		report_skip("need at least 2 cpus for this test");
+		goto error;
+	}
+
+	psw.mask = extract_psw_mask();
+	psw.addr = (unsigned long)test_cmm_during_migration;
+	smp_cpu_setup(1, psw);
+
+	puts("Please migrate me, then press return\n");
+	(void)getchar();
+
+	thread_should_exit = 1;
+
+	while (!thread_exited)
+		mb();
+
+	report_info("thread completed %d iterations", thread_iters);
+
+	report_prefix_push("during migration");
+	if (verification_failure_occured)
+		cmm_report_verify_fail(&result);
+	else
+		report_pass("page states matched");
+	report_prefix_pop();
+
+	/*
+	 * Verification of page states 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 page states which might not have been migrated
+	 * correctly.
+	 */
+	report_prefix_push("after migration");
+	if (!cmm_verify_page_states(pagebuf, NUM_PAGES, &result))
+		cmm_report_verify_fail(&result);
+	else
+		report_pass("page states matched");
+	report_prefix_pop();
+
+	goto done;
+
+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 alltogether.
+	 */
+	puts("Please migrate me, then press return\n");
+	(void)getchar();
+
+done:
+	report_prefix_pop();
+	return report_summary();
+}
diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
index 3caf81eda396..f6889bd4da01 100644
--- a/s390x/unittests.cfg
+++ b/s390x/unittests.cfg
@@ -208,3 +208,8 @@ groups = migration
 [exittime]
 file = exittime.elf
 smp = 2
+
+[migration-during-cmm]
+file = migration-during-cmm.elf
+groups = migration
+smp = 2
-- 
2.36.1

Re: [kvm-unit-tests PATCH v1 1/2] s390x: add a library for CMM-related functions

[Claudio Imbrenda]

On Tue, 22 Nov 2022 17:12:42 +0100
Nico Boehr <nrb@linux.ibm.com> wrote:

> Upcoming changes will add a test which is very similar to the existing
> CMM migration test. To reduce code duplication, move the common function
> to a library which can be re-used by both tests.

I have several (mostly cosmetic) nits

> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> ---
>  lib/s390x/cmm.c       | 83 +++++++++++++++++++++++++++++++++++++++++++
>  lib/s390x/cmm.h       | 29 +++++++++++++++
>  s390x/Makefile        |  1 +
>  s390x/migration-cmm.c | 36 ++++++-------------
>  4 files changed, 123 insertions(+), 26 deletions(-)
>  create mode 100644 lib/s390x/cmm.c
>  create mode 100644 lib/s390x/cmm.h
> 
> diff --git a/lib/s390x/cmm.c b/lib/s390x/cmm.c
> new file mode 100644
> index 000000000000..9609cea68950
> --- /dev/null
> +++ b/lib/s390x/cmm.c
> @@ -0,0 +1,83 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * CMM test library
> + *
> + * Copyright IBM Corp. 2022
> + *
> + * Authors:
> + *  Nico Boehr <nrb@linux.ibm.com>
> + */
> +#include <libcflat.h>
> +#include <bitops.h>
> +#include "cmm.h"
> +
> +/*
> + * Maps ESSA actions to states the page is allowed to be in after the
> + * respective action was executed.
> + */
> +const int allowed_essa_state_masks[4] = {
> +	BIT(ESSA_USAGE_STABLE),					/* ESSA_SET_STABLE */
> +	BIT(ESSA_USAGE_UNUSED),					/* ESSA_SET_UNUSED */
> +	BIT(ESSA_USAGE_VOLATILE),				/* ESSA_SET_VOLATILE */
> +	BIT(ESSA_USAGE_VOLATILE) | BIT(ESSA_USAGE_POT_VOLATILE) /* ESSA_SET_POT_VOLATILE */
> +};
> +
> +static inline unsigned long get_page_addr(uint8_t *pagebuf, int page_idx)

I don't like the name of this function, but maybe you can just get rid
of it (see below)

> +{
> +	return (unsigned long)(pagebuf + PAGE_SIZE * page_idx);
> +}
> +
> +/*
> + * Set CMM page states on pagebuf.
> + * pagebuf must point to page_count consecutive pages.
> + * page_count must be a multiple of 4.
> + */
> +void cmm_set_page_states(uint8_t *pagebuf, int page_count)
> +{

unsigned long addr = (unsigned long)pagebuf;

> +	int i;
> +
> +	assert(page_count % 4 == 0);
> +	for (i = 0; i < page_count; i += 4) {
> +		essa(ESSA_SET_STABLE, get_page_addr(pagebuf, i));

addr + i * PAGE_SIZE

> +		essa(ESSA_SET_UNUSED, get_page_addr(pagebuf, i + 1));

addr + (i + 1) * PAGE_SIZE

> +		essa(ESSA_SET_VOLATILE, get_page_addr(pagebuf, i + 2));

etc

> +		essa(ESSA_SET_POT_VOLATILE, get_page_addr(pagebuf, i + 3));
> +	}
> +}
> +
> +/*
> + * Verify CMM page states on pagebuf.
> + * Page states must have been set by cmm_set_page_states on pagebuf before.
> + * page_count must be a multiple of 4.
> + *
> + * If page states match the expected result,
> + * will return true and result will be untouched. When a mismatch occurs, will
> + * return false and result will be filled with details on the first mismatch.
> + */
> +bool cmm_verify_page_states(uint8_t *pagebuf, int page_count, struct cmm_verify_result *result)
> +{
> +	int i, state_mask, actual_state;

I think "expected_mask" would be a better name, and maybe call the
other one "actual_mask"

> +
> +	assert(page_count % 4 == 0);
> +
> +	for (i = 0; i < page_count; i++) {
> +		actual_state = essa(ESSA_GET_STATE, get_page_addr(pagebuf, i));

addr + i * PAGE_SIZE (if we get rid of get_page_addr)

> +		/* extract the usage state in bits 60 and 61 */
> +		actual_state = (actual_state >> 2) & 0x3;

actual_mask = BIT((actual_mask >> 2) & 3);

> +		state_mask = allowed_essa_state_masks[i % ARRAY_SIZE(allowed_essa_state_masks)];
> +		if (!(BIT(actual_state) & state_mask)) {
> +			result->page_mismatch = i;
> +			result->expected_mask = state_mask;
> +			result->actual_mask = BIT(actual_state);
> +			return false;
> +		}
> +	}
> +
> +	return true;
> +}
> +
> +void cmm_report_verify_fail(struct cmm_verify_result const *result)
> +{
> +	report_fail("page state mismatch: first page = %d, expected_mask = 0x%x, actual_mask = 0x%x", result->page_mismatch, result->expected_mask, result->actual_mask);

it would be a good idea to also print the actual address where the
mismatch was found (with %p and (pagebuf + result->page_mismatch))

> +}
> +
> diff --git a/lib/s390x/cmm.h b/lib/s390x/cmm.h
> new file mode 100644
> index 000000000000..56e188c78704
> --- /dev/null
> +++ b/lib/s390x/cmm.h
> @@ -0,0 +1,29 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * CMM test library
> + *
> + * Copyright IBM Corp. 2022
> + *
> + * Authors:
> + *  Nico Boehr <nrb@linux.ibm.com>
> + */
> +#ifndef S390X_CMM_H
> +#define S390X_CMM_H
> +
> +#include <libcflat.h>
> +#include <asm/page.h>
> +#include <asm/cmm.h>
> +
> +struct cmm_verify_result {
> +	int page_mismatch;
> +	int expected_mask;
> +	int actual_mask;
> +};

I'm not too fond of this, I wonder if it's possible to just return the
struct (maybe make the masks chars, since they will be small)

but I am not sure if the code will actually look better in the end

> +
> +void cmm_set_page_states(uint8_t *pagebuf, int page_count);
> +
> +bool cmm_verify_page_states(uint8_t *pagebuf, int page_count, struct cmm_verify_result *result);
> +
> +void cmm_report_verify_fail(struct cmm_verify_result const *result);
> +
> +#endif /* S390X_CMM_H */
> diff --git a/s390x/Makefile b/s390x/Makefile
> index bf1504f9d58c..401cb6371cee 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -99,6 +99,7 @@ cflatobjs += lib/s390x/malloc_io.o
>  cflatobjs += lib/s390x/uv.o
>  cflatobjs += lib/s390x/sie.o
>  cflatobjs += lib/s390x/fault.o
> +cflatobjs += lib/s390x/cmm.o
>  
>  OBJDIRS += lib/s390x
>  
> diff --git a/s390x/migration-cmm.c b/s390x/migration-cmm.c
> index aa7910ca76bf..ffd656f4db75 100644
> --- a/s390x/migration-cmm.c
> +++ b/s390x/migration-cmm.c
> @@ -14,41 +14,25 @@
>  #include <asm/cmm.h>
>  #include <bitops.h>
>  
> +#include "cmm.h"
> +
>  #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 void test_migration(void)
>  {
> -	int i, state_mask, actual_state;
> -	/*
> -	 * Maps ESSA actions to states the page is allowed to be in after the
> -	 * respective action was executed.
> -	 */
> -	int allowed_essa_state_masks[4] = {
> -		BIT(ESSA_USAGE_STABLE),					/* ESSA_SET_STABLE */
> -		BIT(ESSA_USAGE_UNUSED),					/* ESSA_SET_UNUSED */
> -		BIT(ESSA_USAGE_VOLATILE),				/* ESSA_SET_VOLATILE */
> -		BIT(ESSA_USAGE_VOLATILE) | BIT(ESSA_USAGE_POT_VOLATILE) /* ESSA_SET_POT_VOLATILE */
> -	};
> +	struct cmm_verify_result result = {};
>  
> -	assert(NUM_PAGES % 4 == 0);
> -	for (i = 0; i < NUM_PAGES; i += 4) {
> -		essa(ESSA_SET_STABLE, (unsigned long)pagebuf[i]);
> -		essa(ESSA_SET_UNUSED, (unsigned long)pagebuf[i + 1]);
> -		essa(ESSA_SET_VOLATILE, (unsigned long)pagebuf[i + 2]);
> -		essa(ESSA_SET_POT_VOLATILE, (unsigned long)pagebuf[i + 3]);
> -	}
> +	cmm_set_page_states(pagebuf, NUM_PAGES);
>  
>  	puts("Please migrate me, then press return\n");
>  	(void)getchar();
>  
> -	for (i = 0; i < NUM_PAGES; i++) {
> -		actual_state = essa(ESSA_GET_STATE, (unsigned long)pagebuf[i]);
> -		/* extract the usage state in bits 60 and 61 */
> -		actual_state = (actual_state >> 2) & 0x3;
> -		state_mask = allowed_essa_state_masks[i % ARRAY_SIZE(allowed_essa_state_masks)];
> -		report(BIT(actual_state) & state_mask, "page %d state: expected_mask=0x%x actual_mask=0x%lx", i, state_mask, BIT(actual_state));
> -	}
> +	if (!cmm_verify_page_states(pagebuf, NUM_PAGES, &result))
> +		cmm_report_verify_fail(&result);
> +	else
> +		report_pass("page states match");
>  }
>  
>  int main(void)

Re: [kvm-unit-tests PATCH v1 2/2] s390x: add CMM test during migration

[Claudio Imbrenda]

On Tue, 22 Nov 2022 17:12:43 +0100
Nico Boehr <nrb@linux.ibm.com> wrote:

> Add a test which modifies CMM page states while migration is in
> progress.
> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> ---
>  s390x/Makefile               |   1 +
>  s390x/migration-during-cmm.c | 111 +++++++++++++++++++++++++++++++++++
>  s390x/unittests.cfg          |   5 ++
>  3 files changed, 117 insertions(+)
>  create mode 100644 s390x/migration-during-cmm.c
> 
> diff --git a/s390x/Makefile b/s390x/Makefile
> index 401cb6371cee..64c7c04409ae 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -39,6 +39,7 @@ tests += $(TEST_DIR)/panic-loop-extint.elf
>  tests += $(TEST_DIR)/panic-loop-pgm.elf
>  tests += $(TEST_DIR)/migration-sck.elf
>  tests += $(TEST_DIR)/exittime.elf
> +tests += $(TEST_DIR)/migration-during-cmm.elf
>  
>  pv-tests += $(TEST_DIR)/pv-diags.elf
>  
> diff --git a/s390x/migration-during-cmm.c b/s390x/migration-during-cmm.c
> new file mode 100644
> index 000000000000..3c96283d7b00
> --- /dev/null
> +++ b/s390x/migration-during-cmm.c
> @@ -0,0 +1,111 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Perform CMMA actions while migrating.
> + *
> + * Copyright IBM Corp. 2022
> + *
> + * Authors:
> + *  Nico Boehr <nrb@linux.ibm.com>
> + */
> +
> +#include <libcflat.h>
> +#include <smp.h>
> +#include <asm-generic/barrier.h>
> +
> +#include "cmm.h"
> +
> +#define NUM_PAGES 128

is 128 enough to allow multiple iterations of the thread?

> +
> +static uint8_t pagebuf[NUM_PAGES * PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
> +
> +static int thread_iters;

please make all ints unsigned unless you really need them signed

> +static int thread_should_exit;
> +static int thread_exited;

(these are fine as is, since they are only used as flags)

> +static bool verification_failure_occured;
> +struct cmm_verify_result result;
> +
> +static void test_cmm_during_migration(void)
> +{
> +	/*
> +	 * The second CPU must not print on the console, otherwise it will race with
> +	 * the primary CPU on the SCLP buffer.
> +	 */
> +	while (!thread_should_exit) {
> +		cmm_set_page_states(pagebuf, NUM_PAGES);

I would do (pagebuf + (thread_iters % 4) * PAGE_SIZE

this way you will actually change the values for each page at each
iteration (will need a bigger buffer)

> +		if (!cmm_verify_page_states(pagebuf, NUM_PAGES, &result)) {
> +			verification_failure_occured = true;
> +			goto out;
> +		}
> +		thread_iters++;
> +	}
> +
> +out:
> +	thread_exited = 1;
> +}
> +
> +int main(void)
> +{
> +	bool has_essa = check_essa_available();
> +	struct psw psw;
> +
> +	report_prefix_push("migration-during-cmm");
> +	if (!has_essa) {
> +		report_skip("ESSA is not available");
> +		goto error;
> +	}
> +
> +	if (smp_query_num_cpus() == 1) {
> +		report_skip("need at least 2 cpus for this test");
> +		goto error;
> +	}
> +
> +	psw.mask = extract_psw_mask();
> +	psw.addr = (unsigned long)test_cmm_during_migration;
> +	smp_cpu_setup(1, psw);
> +
> +	puts("Please migrate me, then press return\n");
> +	(void)getchar();
> +
> +	thread_should_exit = 1;

I would use WRITE_ONCE, otherwise you probably need a mb() here

> +
> +	while (!thread_exited)
> +		mb();
> +
> +	report_info("thread completed %d iterations", thread_iters);
> +
> +	report_prefix_push("during migration");
> +	if (verification_failure_occured)
> +		cmm_report_verify_fail(&result);
> +	else
> +		report_pass("page states matched");
> +	report_prefix_pop();
> +
> +	/*
> +	 * Verification of page states 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 page states which might not have been migrated
> +	 * correctly.
> +	 */
> +	report_prefix_push("after migration");
> +	if (!cmm_verify_page_states(pagebuf, NUM_PAGES, &result))

pagebuf + ((thread_iters - 1) % 4) * PAGE_SIZE

> +		cmm_report_verify_fail(&result);
> +	else
> +		report_pass("page states matched");
> +	report_prefix_pop();
> +
> +	goto done;
> +
> +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 alltogether.
> +	 */
> +	puts("Please migrate me, then press return\n");
> +	(void)getchar();
> +
> +done:
> +	report_prefix_pop();
> +	return report_summary();
> +}
> diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
> index 3caf81eda396..f6889bd4da01 100644
> --- a/s390x/unittests.cfg
> +++ b/s390x/unittests.cfg
> @@ -208,3 +208,8 @@ groups = migration
>  [exittime]
>  file = exittime.elf
>  smp = 2
> +
> +[migration-during-cmm]
> +file = migration-during-cmm.elf
> +groups = migration
> +smp = 2

Re: [kvm-unit-tests PATCH v1 1/2] s390x: add a library for CMM-related functions

[Nico Boehr]

Quoting Claudio Imbrenda (2022-11-23 13:13:38)
> > diff --git a/lib/s390x/cmm.c b/lib/s390x/cmm.c
> > new file mode 100644
> > index 000000000000..9609cea68950
[...]
> > +static inline unsigned long get_page_addr(uint8_t *pagebuf, int page_idx)
> 
> I don't like the name of this function, but maybe you can just get rid
> of it (see below)

Didn't like repeating the cast with the address calculation every time, but your solution with the cast first is good too. Done.

[...]
> > +/*
> > + * Verify CMM page states on pagebuf.
> > + * Page states must have been set by cmm_set_page_states on pagebuf before.
> > + * page_count must be a multiple of 4.
> > + *
> > + * If page states match the expected result,
> > + * will return true and result will be untouched. When a mismatch occurs, will
> > + * return false and result will be filled with details on the first mismatch.
> > + */
> > +bool cmm_verify_page_states(uint8_t *pagebuf, int page_count, struct cmm_verify_result *result)
> > +{
> > +     int i, state_mask, actual_state;
> 
> I think "expected_mask" would be a better name, and maybe call the
> other one "actual_mask"

Yes, makes perfect sense. Done.

> > +
> > +     assert(page_count % 4 == 0);
> > +
> > +     for (i = 0; i < page_count; i++) {
> > +             actual_state = essa(ESSA_GET_STATE, get_page_addr(pagebuf, i));
> 
> addr + i * PAGE_SIZE (if we get rid of get_page_addr)
> 
> > +             /* extract the usage state in bits 60 and 61 */
> > +             actual_state = (actual_state >> 2) & 0x3;
> 
> actual_mask = BIT((actual_mask >> 2) & 3);

Yes makes sense, I will also adjust the comment a bit.

[...]
> > +void cmm_report_verify_fail(struct cmm_verify_result const *result)
> > +{
> > +     report_fail("page state mismatch: first page = %d, expected_mask = 0x%x, actual_mask = 0x%x", result->page_mismatch, result->expected_mask, result->actual_mask);
> 
> it would be a good idea to also print the actual address where the
> mismatch was found (with %p and (pagebuf + result->page_mismatch))

pagebuf is not available here, I want to avoid adding another argument, so I'll add a new field for the address in cmm_verify_result.

> > diff --git a/lib/s390x/cmm.h b/lib/s390x/cmm.h
> > new file mode 100644
> > index 000000000000..56e188c78704
[...]
> > +struct cmm_verify_result {
> > +     int page_mismatch;
> > +     int expected_mask;
> > +     int actual_mask;
> > +};
> 
> I'm not too fond of this, I wonder if it's possible to just return the
> struct (maybe make the masks chars, since they will be small)

No real reason to optimize for size, but also no reason not to, so I just changed it.

> but I am not sure if the code will actually look better in the end

I am not a fan of returning structs, but none of my arguments against it apply
here, so I changed it. Will add a field verify_failed to cmm_verify_result. 

This has the nice side effect that I don't have to do 
  if(cmm_verify_page_states()) 
    report_pass()
  else
    cmm_report_verify_fail()
in every caller, but can just move this whole logic to a function.

Re: [kvm-unit-tests PATCH v1 1/2] s390x: add a library for CMM-related functions

[Claudio Imbrenda]

On Wed, 23 Nov 2022 17:12:52 +0100
Nico Boehr <nrb@linux.ibm.com> wrote:

> Quoting Claudio Imbrenda (2022-11-23 13:13:38)
> > > diff --git a/lib/s390x/cmm.c b/lib/s390x/cmm.c
> > > new file mode 100644
> > > index 000000000000..9609cea68950  
> [...]
> > > +static inline unsigned long get_page_addr(uint8_t *pagebuf, int page_idx)  
> > 
> > I don't like the name of this function, but maybe you can just get rid
> > of it (see below)  
> 
> Didn't like repeating the cast with the address calculation every time, but your solution with the cast first is good too. Done.
> 
> [...]
> > > +/*
> > > + * Verify CMM page states on pagebuf.
> > > + * Page states must have been set by cmm_set_page_states on pagebuf before.
> > > + * page_count must be a multiple of 4.
> > > + *
> > > + * If page states match the expected result,
> > > + * will return true and result will be untouched. When a mismatch occurs, will
> > > + * return false and result will be filled with details on the first mismatch.
> > > + */
> > > +bool cmm_verify_page_states(uint8_t *pagebuf, int page_count, struct cmm_verify_result *result)
> > > +{
> > > +     int i, state_mask, actual_state;  
> > 
> > I think "expected_mask" would be a better name, and maybe call the
> > other one "actual_mask"  
> 
> Yes, makes perfect sense. Done.
> 
> > > +
> > > +     assert(page_count % 4 == 0);
> > > +
> > > +     for (i = 0; i < page_count; i++) {
> > > +             actual_state = essa(ESSA_GET_STATE, get_page_addr(pagebuf, i));  
> > 
> > addr + i * PAGE_SIZE (if we get rid of get_page_addr)
> >   
> > > +             /* extract the usage state in bits 60 and 61 */
> > > +             actual_state = (actual_state >> 2) & 0x3;  
> > 
> > actual_mask = BIT((actual_mask >> 2) & 3);  
> 
> Yes makes sense, I will also adjust the comment a bit.
> 
> [...]
> > > +void cmm_report_verify_fail(struct cmm_verify_result const *result)
> > > +{
> > > +     report_fail("page state mismatch: first page = %d, expected_mask = 0x%x, actual_mask = 0x%x", result->page_mismatch, result->expected_mask, result->actual_mask);  
> > 
> > it would be a good idea to also print the actual address where the
> > mismatch was found (with %p and (pagebuf + result->page_mismatch))  
> 
> pagebuf is not available here, I want to avoid adding another argument, so I'll add a new field for the address in cmm_verify_result.
> 
> > > diff --git a/lib/s390x/cmm.h b/lib/s390x/cmm.h
> > > new file mode 100644
> > > index 000000000000..56e188c78704  
> [...]
> > > +struct cmm_verify_result {
> > > +     int page_mismatch;
> > > +     int expected_mask;
> > > +     int actual_mask;
> > > +};  
> > 
> > I'm not too fond of this, I wonder if it's possible to just return the
> > struct (maybe make the masks chars, since they will be small)  
> 
> No real reason to optimize for size, but also no reason not to, so I just changed it.
> 
> > but I am not sure if the code will actually look better in the end  
> 
> I am not a fan of returning structs, but none of my arguments against it apply
> here, so I changed it. Will add a field verify_failed to cmm_verify_result. 

I'm not sure I follow, but I guess I'll see it in v2

just make sure the code is not uglier, otherwise it's pointless :)

> 
> This has the nice side effect that I don't have to do 
>   if(cmm_verify_page_states()) 
>     report_pass()
>   else
>     cmm_report_verify_fail()
> in every caller, but can just move this whole logic to a function.

Re: [kvm-unit-tests PATCH v1 2/2] s390x: add CMM test during migration

[Nico Boehr]

Quoting Claudio Imbrenda (2022-11-23 13:25:55)
[...]
> > diff --git a/s390x/migration-during-cmm.c b/s390x/migration-during-cmm.c
> > new file mode 100644
> > index 000000000000..3c96283d7b00
> > --- /dev/null
> > +++ b/s390x/migration-during-cmm.c
> > @@ -0,0 +1,111 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Perform CMMA actions while migrating.
> > + *
> > + * Copyright IBM Corp. 2022
> > + *
> > + * Authors:
> > + *  Nico Boehr <nrb@linux.ibm.com>
> > + */
> > +
> > +#include <libcflat.h>
> > +#include <smp.h>
> > +#include <asm-generic/barrier.h>
> > +
> > +#include "cmm.h"
> > +
> > +#define NUM_PAGES 128
> 
> is 128 enough to allow multiple iterations of the thread?

Enough for about 16.000 iterations on my box :)