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selftests/powerpc: Relax L1d miss targets for rfi_flush test

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When running the rfi_flush test, if the system is loaded, we see two
issues:
1. The L1d misses when rfi_flush is disabled increase significantly due
to other workloads interfering with the cache.
2. The L1d misses when rfi_flush is enabled sometimes goes slightly
below the expected number of misses.

To address these, let's relax the expected number of L1d misses:
1. When rfi_flush is disabled, we allow upto half the expected number of
the misses for when rfi_flush is enabled.
2. When rfi_flush is enabled, we allow ~1% lower number of cache misses.

Reported-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Tested-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Naveen N. Rao 2018-10-23 13:34:56 +05:30 committed by Michael Ellerman
parent 3b9672fff7
commit a95ecac5cb
1 changed files with 13 additions and 5 deletions
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18
tools/testing/selftests/powerpc/security/rfi_flush.c
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@ -49,6 +49,7 @@ int rfi_flush_test(void)
struct perf_event_read v;
__u64 l1d_misses_total = 0;
unsigned long iterations = 100000, zero_size = 24 * 1024;
unsigned long l1d_misses_expected;
int rfi_flush_org, rfi_flush;
SKIP_IF(geteuid() != 0);
@ -71,6 +72,12 @@ int rfi_flush_test(void)
iter = repetitions;
/*
* We expect to see l1d miss for each cacheline access when rfi_flush
* is set. Allow a small variation on this.
*/
l1d_misses_expected = iterations * (zero_size / CACHELINE_SIZE - 2);
again:
FAIL_IF(perf_event_reset(fd));
@ -78,10 +85,9 @@ again:
FAIL_IF(read(fd, &v, sizeof(v)) != sizeof(v));
/* Expect at least zero_size/CACHELINE_SIZE misses per iteration */
if (v.l1d_misses >= (iterations * zero_size / CACHELINE_SIZE) && rfi_flush)
if (rfi_flush && v.l1d_misses >= l1d_misses_expected)
passes++;
else if (v.l1d_misses < iterations && !rfi_flush)
else if (!rfi_flush && v.l1d_misses < (l1d_misses_expected / 2))
passes++;
l1d_misses_total += v.l1d_misses;
@ -92,13 +98,15 @@ again:
if (passes < repetitions) {
printf("FAIL (L1D misses with rfi_flush=%d: %llu %c %lu) [%d/%d failures]\n",
rfi_flush, l1d_misses_total, rfi_flush ? '<' : '>',
rfi_flush ? (repetitions * iterations * zero_size / CACHELINE_SIZE) : iterations,
rfi_flush ? repetitions * l1d_misses_expected :
repetitions * l1d_misses_expected / 2,
repetitions - passes, repetitions);
rc = 1;
} else
printf("PASS (L1D misses with rfi_flush=%d: %llu %c %lu) [%d/%d pass]\n",
rfi_flush, l1d_misses_total, rfi_flush ? '>' : '<',
rfi_flush ? (repetitions * iterations * zero_size / CACHELINE_SIZE) : iterations,
rfi_flush ? repetitions * l1d_misses_expected :
repetitions * l1d_misses_expected / 2,
passes, repetitions);
if (rfi_flush == rfi_flush_org) {