Re: [kvm-unit-tests PATCH v4 1/1] s390x: add migration test for storage keys

[Janosch Frank <frankja@linux.ibm.com>]

On 6/8/22 15:13, Nico Boehr wrote:
> Upon migration, we expect storage keys set by the guest to be preserved, so add
> a test for it.
> 
> We keep 128 pages and set predictable storage keys. Then, we migrate and check
> that they can be read back and match the value originally set.
> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> ---
>   s390x/Makefile         |  1 +
>   s390x/migration-skey.c | 73 ++++++++++++++++++++++++++++++++++++++++++
>   s390x/unittests.cfg    |  4 +++
>   3 files changed, 78 insertions(+)
>   create mode 100644 s390x/migration-skey.c
> 
> diff --git a/s390x/Makefile b/s390x/Makefile
> index 25802428fa13..94fc5c1a3527 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -33,6 +33,7 @@ tests += $(TEST_DIR)/adtl-status.elf
>   tests += $(TEST_DIR)/migration.elf
>   tests += $(TEST_DIR)/pv-attest.elf
>   tests += $(TEST_DIR)/migration-cmm.elf
> +tests += $(TEST_DIR)/migration-skey.elf
>   
>   pv-tests += $(TEST_DIR)/pv-diags.elf
>   
> diff --git a/s390x/migration-skey.c b/s390x/migration-skey.c
> new file mode 100644
> index 000000000000..323aa83202bb
> --- /dev/null
> +++ b/s390x/migration-skey.c
> @@ -0,0 +1,73 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Storage Key migration tests
> + *
> + * Copyright IBM Corp. 2022
> + *
> + * Authors:
> + *  Nico Boehr <nrb@linux.ibm.com>
> + */
> +
> +#include <libcflat.h>
> +#include <asm/facility.h>
> +#include <asm/page.h>
> +#include <asm/mem.h>
> +#include <asm/interrupt.h>
> +#include <hardware.h>
> +
> +#define NUM_PAGES 128
> +static uint8_t pagebuf[NUM_PAGES][PAGE_SIZE] __attribute__((aligned(PAGE_SIZE)));
> +
> +static void test_migration(void)
> +{
> +	union skey expected_key, actual_key;
> +	int i, key_to_set;
> +
> +	for (i = 0; i < NUM_PAGES; i++) {
> +		/*
> +		 * Storage keys are 7 bit, lowest bit is always returned as zero
> +		 * by iske
> +		 */

Maybe add:
This loop will set all 7 bits which means we set fetch 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);
> +	}
> +
> +	puts("Please migrate me, then press return\n");
> +	(void)getchar();
> +
> +	for (i = 0; i < NUM_PAGES; i++) {
> +		report_prefix_pushf("page %d", i);
> +
> +		actual_key.val = get_storage_key(pagebuf[i]);

iske is nice but I think it would also be interesting to check if the 
actual memory protection was carried over. The iske check is enough for 
now though.

> +		expected_key.val = i * 2;
> +
> +		/* ignore reference bit */
> +		actual_key.str.rf = 0;
> +		expected_key.str.rf = 0;
> +
> +		report(actual_key.val == expected_key.val, "expected_key=0x%x actual_key=0x%x", expected_key.val, actual_key.val);

This spams the log with useless information and hence I generally try to 
avoid printing large loops.

Instead we should print all fails or a simple success message if all 
comparisons were successful.

> +
> +		report_prefix_pop();
> +	}
> +}
> +
> +int main(void)
> +{
> +	report_prefix_push("migration-skey");
> +	if (test_facility(169)) {
> +		report_skip("storage key removal facility is active");
> +
> +		/*
> +		 * 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();
> +	} else {
> +		test_migration();
> +	}
> +
> +	report_prefix_pop();
> +	return report_summary();
> +}
> diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
> index 9b97d0471bcf..8e52f560bb1e 100644
> --- a/s390x/unittests.cfg
> +++ b/s390x/unittests.cfg
> @@ -180,3 +180,7 @@ smp = 2
>   [migration-cmm]
>   file = migration-cmm.elf
>   groups = migration
> +
> +[migration-skey]
> +file = migration-skey.elf
> +groups = migration