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

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

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)