Re: [kvm-unit-tests PATCH v5 1/1] s390x: add CMM test during migration

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Tue, 20 Dec 2022 10:19:23 +0100
Nico Boehr <nrb@linux.ibm.com> wrote:

> Add a test which modifies CMM page states while migration is in
> progress.
> 
> This is added to the existing migration-cmm test, which gets a new
> command line argument for the sequential and parallel variants.
> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  s390x/migration-cmm.c | 258 +++++++++++++++++++++++++++++++++++++-----
>  s390x/unittests.cfg   |  15 ++-
>  2 files changed, 240 insertions(+), 33 deletions(-)
> 
> diff --git a/s390x/migration-cmm.c b/s390x/migration-cmm.c
> index 43673f18e45a..8855069f05f9 100644
> --- a/s390x/migration-cmm.c
> +++ b/s390x/migration-cmm.c
> @@ -2,6 +2,12 @@
>  /*
>   * CMM migration tests (ESSA)
>   *
> + * There are two variants of this test:
> + * - sequential: sets the CMM page states, then migrates the VM and - after
> + *   migration finished - verifies the page states have been preserved.
> + * - parallel: migrate the VM and - while migration is in progress - change the
> + *   page states and verify they are preserved.
> + *
>   * Copyright IBM Corp. 2022
>   *
>   * Authors:
> @@ -13,55 +19,249 @@
>  #include <asm/interrupt.h>
>  #include <asm/page.h>
>  #include <asm/cmm.h>
> +#include <asm/barrier.h>
>  #include <bitops.h>
> +#include <smp.h>
> +
> +struct verify_result {
> +	bool verify_failed;
> +	char expected_mask;
> +	char actual_mask;
> +	unsigned long page_mismatch_idx;
> +	unsigned long page_mismatch_addr;
> +};
> +
> +static enum {
> +	TEST_INVLALID,
> +	TEST_SEQUENTIAL,
> +	TEST_PARALLEL
> +} arg_test_to_run;
>  
>  #define NUM_PAGES 128
> -static uint8_t pagebuf[NUM_PAGES][PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
>  
> -static void test_migration(void)
> +/*
> + * Allocate 3 pages more than we need so we can start at different offsets.
> + * For the parallel test, this ensures page states change on every loop iteration.
> + */
> +static uint8_t pagebuf[(NUM_PAGES + 3) * PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
> +
> +static struct verify_result result;
> +
> +static unsigned int thread_iters;
> +static int thread_should_exit;
> +static int thread_exited;
> +
> +/*
> + * Maps ESSA actions to states the page is allowed to be in after the
> + * respective action was executed.
> + */
> +static const unsigned long 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 */
> +};
> +
> +/*
> + * Set CMM page state test pattern on pagebuf.
> + * pagebuf must point to page_count consecutive pages.
> + * page_count must be a multiple of 4.
> + */
> +static void set_test_pattern(uint8_t *pagebuf, size_t page_count)
> +{
> +	unsigned long addr = (unsigned long)pagebuf;
> +	size_t i;
> +
> +	assert(page_count % 4 == 0);
> +	for (i = 0; i < page_count; i += 4) {
> +		essa(ESSA_SET_STABLE, addr + i * PAGE_SIZE);
> +		essa(ESSA_SET_UNUSED, addr + (i + 1) * PAGE_SIZE);
> +		essa(ESSA_SET_VOLATILE, addr + (i + 2) * PAGE_SIZE);
> +		essa(ESSA_SET_POT_VOLATILE, addr + (i + 3) * PAGE_SIZE);
> +	}
> +}
> +
> +/*
> + * Verify CMM page states on pagebuf.
> + * Page states must have been set by set_test_pattern on pagebuf before.
> + * page_count must be a multiple of 4.
> + *
> + * If page states match the expected result, will return a verify_result
> + * with verify_failed false. All other fields are then invalid.
> + * If there is a mismatch, the returned struct will have verify_failed true
> + * and will be filled with details on the first mismatch encountered.
> + */
> +static struct verify_result verify_page_states(uint8_t *pagebuf, size_t page_count)
> +{
> +	unsigned long expected_mask, actual_mask;
> +	struct verify_result result = {
> +		.verify_failed = true
> +	};
> +	unsigned long addr;
> +	size_t i;
> +
> +	assert(page_count % 4 == 0);
> +	for (i = 0; i < page_count; i++) {
> +		addr = (unsigned long)(pagebuf + i * PAGE_SIZE);
> +		actual_mask = essa(ESSA_GET_STATE, addr);
> +		/* usage state in bits 60 and 61 */
> +		actual_mask = BIT((actual_mask >> 2) & 0x3);
> +		expected_mask = allowed_essa_state_masks[i % ARRAY_SIZE(allowed_essa_state_masks)];
> +		if (!(actual_mask & expected_mask)) {
> +			result.page_mismatch_idx = i;
> +			result.page_mismatch_addr = addr;
> +			result.expected_mask = expected_mask;
> +			result.actual_mask = actual_mask;
> +			return result;
> +		}
> +	}
> +
> +	result.verify_failed = false;
> +	return result;
> +}
> +
> +static void report_verify_result(const struct verify_result *result)
> +{
> +	if (result->verify_failed)
> +		report_fail("page state mismatch: first page idx = %lu, addr = %lx, "
> +			"expected_mask = 0x%x, actual_mask = 0x%x",
> +			result->page_mismatch_idx, result->page_mismatch_addr,
> +			result->expected_mask, result->actual_mask);
> +	else
> +		report_pass("page states match");
> +}
> +
> +static void test_cmm_migration_sequential(void)
> +{
> +	report_prefix_push("sequential");
> +
> +	set_test_pattern(pagebuf, NUM_PAGES);
> +
> +	migrate_once();
> +
> +	result = verify_page_states(pagebuf, NUM_PAGES);
> +	report_verify_result(&result);
> +
> +	report_prefix_pop();
> +}
> +
> +static void set_cmm_thread(void)
>  {
> -	int i, state_mask, actual_state;
> +	uint8_t *pagebuf_start;
>  	/*
> -	 * Maps ESSA actions to states the page is allowed to be in after the
> -	 * respective action was executed.
> +	 * The second CPU must not print to the console, otherwise it will race with
> +	 * the primary CPU on the SCLP buffer.
>  	 */
> -	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 */
> -	};
> +	while (!READ_ONCE(thread_should_exit)) {
> +		/*
> +		 * Start on a offset different from the last iteration so page states change with
> +		 * every iteration. This is why pagebuf has 3 extra pages.
> +		 */
> +		pagebuf_start = pagebuf + (thread_iters % 4) * PAGE_SIZE;
> +		set_test_pattern(pagebuf_start, NUM_PAGES);
> +
> +		/*
> +		 * 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++;
>  
> -	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]);
> +		result = verify_page_states(pagebuf_start, NUM_PAGES);
> +		if (result.verify_failed)
> +			break;
>  	}
>  
> +	WRITE_ONCE(thread_exited, 1);
> +}
> +
> +static void test_cmm_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_cmm_thread));
> +
>  	migrate_once();
>  
> -	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));
> +	WRITE_ONCE(thread_should_exit, 1);
> +
> +	while (!READ_ONCE(thread_exited))
> +		;
> +
> +	/* Ensure thread_iters and result below are read from memory after thread completed */
> +	mb();
> +
> +	report_info("thread completed %u iterations", thread_iters);
> +
> +	report_prefix_push("during migration");
> +	report_verify_result(&result);
> +	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");
> +	assert(thread_iters > 0);
> +	result = verify_page_states(pagebuf + ((thread_iters - 1) % 4) * PAGE_SIZE, NUM_PAGES);
> +	report_verify_result(&result);
> +	report_prefix_pop();
> +
> +error:
> +	report_prefix_pop();
> +}
> +
> +static void print_usage(void)
> +{
> +	report_info("Usage: migration-cmm [--parallel|--sequential]");
> +}
> +
> +static void parse_args(int argc, char **argv)
> +{
> +	if (argc < 2) {
> +		/* default to sequential since it only needs one CPU */
> +		arg_test_to_run = TEST_SEQUENTIAL;
> +		return;
>  	}
> +
> +	if (!strcmp("--parallel", argv[1]))
> +		arg_test_to_run = TEST_PARALLEL;
> +	else if (!strcmp("--sequential", argv[1]))
> +		arg_test_to_run = TEST_SEQUENTIAL;
> +	else
> +		arg_test_to_run = TEST_INVLALID;
>  }
>  
> -int main(void)
> +int main(int argc, char **argv)
>  {
>  	report_prefix_push("migration-cmm");
> -
> -	if (!check_essa_available())
> +	if (!check_essa_available()) {
>  		report_skip("ESSA is not available");
> -	else
> -		test_migration();
> +		goto error;
> +	}
>  
> -	migrate_once();
> +	parse_args(argc, argv);
> +
> +	switch (arg_test_to_run) {
> +	case TEST_SEQUENTIAL:
> +		test_cmm_migration_sequential();
> +	break;
> +	case TEST_PARALLEL:
> +		test_cmm_migration_parallel();
> +	break;
> +	default:
> +		print_usage();
> +	}
>  
> +error:
> +	migrate_once();
>  	report_prefix_pop();
>  	return report_summary();
>  }
> diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
> index 3caf81eda396..a16c9682e638 100644
> --- a/s390x/unittests.cfg
> +++ b/s390x/unittests.cfg
> @@ -181,10 +181,6 @@ file = migration.elf
>  groups = migration
>  smp = 2
>  
> -[migration-cmm]
> -file = migration-cmm.elf
> -groups = migration
> -
>  [migration-skey]
>  file = migration-skey.elf
>  groups = migration
> @@ -208,3 +204,14 @@ groups = migration
>  [exittime]
>  file = exittime.elf
>  smp = 2
> +
> +[migration-cmm-sequential]
> +file = migration-cmm.elf
> +groups = migration
> +extra_params = -append '--sequential'
> +
> +[migration-cmm-parallel]
> +file = migration-during-cmm.elf
> +groups = migration
> +smp = 2
> +extra_params = -append '--parallel'