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From: Eric Auger <eric.auger@redhat.com>
To: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: eric.auger.pro@gmail.com, kvm@vger.kernel.org,
	kvmarm@lists.linux.dev, andrew.jones@linux.dev, maz@kernel.org,
	will@kernel.org, oliver.upton@linux.dev, ricarkol@google.com,
	reijiw@google.com
Subject: Re: [kvm-unit-tests PATCH 2/6] arm: pmu: pmu-chain-promotion: Introduce defines for count and margin values
Date: Mon, 24 Apr 2023 22:09:37 +0200	[thread overview]
Message-ID: <e518045c-6138-f9b7-7503-3b3b47c7ee80@redhat.com> (raw)
In-Reply-To: <ZEJdpmTSyf6sp3Yv@monolith.localdoman>

Hi Alexandru,
On 4/21/23 11:55, Alexandru Elisei wrote:
> Hi,
>
> On Wed, Mar 15, 2023 at 12:07:21PM +0100, Eric Auger wrote:
>> The pmu-chain-promotion test is composed of separate subtests.
>>
>> Some of them apply some settings on a first MEM_ACCESS loop
>> iterations, change the settings and run another MEM_ACCESS loop.
>>
>> The PRE_OVERFLOW2 MEM_ACCESS counter init value is defined so that
>> the first loop does not overflow and the second loop overflows.
>>
>> At the moment the MEM_ACCESS count number is hardcoded to 20 and
>> PRE_OVERFLOW2 is set to UINT32_MAX - 20 - 15 where 15 acts as a
>> margin.
>>
>> Introduce defines for the count number and the margin so that it
>> becomes easier to change them.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> ---
>>  arm/pmu.c | 35 +++++++++++++++++++++--------------
>>  1 file changed, 21 insertions(+), 14 deletions(-)
>>
>> diff --git a/arm/pmu.c b/arm/pmu.c
>> index dad7d4b4..b88366a8 100644
>> --- a/arm/pmu.c
>> +++ b/arm/pmu.c
>> @@ -55,11 +55,18 @@
>>  #define EXT_COMMON_EVENTS_LOW	0x4000
>>  #define EXT_COMMON_EVENTS_HIGH	0x403F
>>  
>> -#define ALL_SET_32			0x00000000FFFFFFFFULL
>> +#define ALL_SET_32		0x00000000FFFFFFFFULL
>>  #define ALL_CLEAR		0x0000000000000000ULL
>>  #define PRE_OVERFLOW_32		0x00000000FFFFFFF0ULL
>> -#define PRE_OVERFLOW2_32	0x00000000FFFFFFDCULL
>>  #define PRE_OVERFLOW_64		0xFFFFFFFFFFFFFFF0ULL
>> +#define COUNT 20
> test_mem_access (from the test "pmu-mem-access") also uses 20 for
> mem_access_loop, in case you want to change the define there too.
I hesitated to change this but in fact the mem-access test does not
suffer the same flaw and there is no risk we don't overflow when we set
to PRE_OVERFLOW init value as the measure is always larger than 20. so I
decided to keep the hardcoded value in that case.
>
> I realize I'm bikeshedding here, but it might also help if the define name
> held some clue to what is being counted (like ACCESS_COUNT, or something
> like that).
the event which is tested is MEM_ACCESS, that's whence the current name
stems from.
>
>> +#define MARGIN 15
>> +/*
>> + * PRE_OVERFLOW2 is set so that 1st COUNT iterations do not
>> + * produce 32b overflow and 2d COUNT iterations do. To accommodate
> 2**nd** COUNT iterations?
OK
>
>> + * for some observed variability we take into account a given @MARGIN
> Some inconsistency here, this variable is referred to with @MARGIN, but
> COUNT isn't (missing "@").
OK
>
>> + */
>> +#define PRE_OVERFLOW2_32		(ALL_SET_32 - COUNT - MARGIN)
> This is much better, I would have been hard pressed to figure out where the
> previous value of 0x00000000FFFFFFDCULL came from.
>
> The patch looks good to me (with or without the comments above):
>
> Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
thanks

Eric
>
> Thanks,
> Alex
>
>>  
>>  #define PRE_OVERFLOW(__overflow_at_64bits)				\
>>  	(__overflow_at_64bits ? PRE_OVERFLOW_64 : PRE_OVERFLOW_32)
>> @@ -737,7 +744,7 @@ static void test_chain_promotion(bool unused)
>>  	write_sysreg_s(0x2, PMCNTENSET_EL0);
>>  	isb();
>>  
>> -	mem_access_loop(addr, 20, pmu.pmcr_ro | PMU_PMCR_E);
>> +	mem_access_loop(addr, COUNT, pmu.pmcr_ro | PMU_PMCR_E);
>>  	PRINT_REGS("post");
>>  	report(!read_regn_el0(pmevcntr, 0),
>>  		"chain counter not counting if even counter is disabled");
>> @@ -750,13 +757,13 @@ static void test_chain_promotion(bool unused)
>>  	write_sysreg_s(0x1, PMCNTENSET_EL0);
>>  	isb();
>>  
>> -	mem_access_loop(addr, 20, pmu.pmcr_ro | PMU_PMCR_E);
>> +	mem_access_loop(addr, COUNT, pmu.pmcr_ro | PMU_PMCR_E);
>>  	PRINT_REGS("post");
>>  	report(!read_regn_el0(pmevcntr, 1) && (read_sysreg(pmovsclr_el0) == 0x1),
>>  		"odd counter did not increment on overflow if disabled");
>>  	report_prefix_pop();
>>  
>> -	/* start at 0xFFFFFFDC, +20 with CHAIN enabled, +20 with CHAIN disabled */
>> +	/* 1st COUNT with CHAIN enabled, next COUNT with CHAIN disabled */
>>  	report_prefix_push("subtest3");
>>  	pmu_reset();
>>  	write_sysreg_s(0x3, PMCNTENSET_EL0);
>> @@ -764,12 +771,12 @@ static void test_chain_promotion(bool unused)
>>  	isb();
>>  	PRINT_REGS("init");
>>  
>> -	mem_access_loop(addr, 20, pmu.pmcr_ro | PMU_PMCR_E);
>> +	mem_access_loop(addr, COUNT, pmu.pmcr_ro | PMU_PMCR_E);
>>  	PRINT_REGS("After 1st loop");
>>  
>>  	/* disable the CHAIN event */
>>  	write_sysreg_s(0x2, PMCNTENCLR_EL0);
>> -	mem_access_loop(addr, 20, pmu.pmcr_ro | PMU_PMCR_E);
>> +	mem_access_loop(addr, COUNT, pmu.pmcr_ro | PMU_PMCR_E);
>>  	PRINT_REGS("After 2d loop");
>>  	report(read_sysreg(pmovsclr_el0) == 0x1,
>>  		"should have triggered an overflow on #0");
>> @@ -777,7 +784,7 @@ static void test_chain_promotion(bool unused)
>>  		"CHAIN counter #1 shouldn't have incremented");
>>  	report_prefix_pop();
>>  
>> -	/* start at 0xFFFFFFDC, +20 with CHAIN disabled, +20 with CHAIN enabled */
>> +	/* 1st COUNT with CHAIN disabled, next COUNT with CHAIN enabled */
>>  
>>  	report_prefix_push("subtest4");
>>  	pmu_reset();
>> @@ -786,13 +793,13 @@ static void test_chain_promotion(bool unused)
>>  	isb();
>>  	PRINT_REGS("init");
>>  
>> -	mem_access_loop(addr, 20, pmu.pmcr_ro | PMU_PMCR_E);
>> +	mem_access_loop(addr, COUNT, pmu.pmcr_ro | PMU_PMCR_E);
>>  	PRINT_REGS("After 1st loop");
>>  
>>  	/* enable the CHAIN event */
>>  	write_sysreg_s(0x3, PMCNTENSET_EL0);
>>  	isb();
>> -	mem_access_loop(addr, 20, pmu.pmcr_ro | PMU_PMCR_E);
>> +	mem_access_loop(addr, COUNT, pmu.pmcr_ro | PMU_PMCR_E);
>>  
>>  	PRINT_REGS("After 2d loop");
>>  
>> @@ -811,7 +818,7 @@ static void test_chain_promotion(bool unused)
>>  	isb();
>>  	PRINT_REGS("init");
>>  
>> -	mem_access_loop(addr, 20, pmu.pmcr_ro | PMU_PMCR_E);
>> +	mem_access_loop(addr, COUNT, pmu.pmcr_ro | PMU_PMCR_E);
>>  	PRINT_REGS("After 1st loop");
>>  
>>  	/* 0 becomes CHAINED */
>> @@ -820,7 +827,7 @@ static void test_chain_promotion(bool unused)
>>  	write_sysreg_s(0x3, PMCNTENSET_EL0);
>>  	write_regn_el0(pmevcntr, 1, 0x0);
>>  
>> -	mem_access_loop(addr, 20, pmu.pmcr_ro | PMU_PMCR_E);
>> +	mem_access_loop(addr, COUNT, pmu.pmcr_ro | PMU_PMCR_E);
>>  	PRINT_REGS("After 2d loop");
>>  
>>  	report((read_regn_el0(pmevcntr, 1) == 1) &&
>> @@ -837,14 +844,14 @@ static void test_chain_promotion(bool unused)
>>  	write_sysreg_s(0x3, PMCNTENSET_EL0);
>>  	PRINT_REGS("init");
>>  
>> -	mem_access_loop(addr, 20, pmu.pmcr_ro | PMU_PMCR_E);
>> +	mem_access_loop(addr, COUNT, pmu.pmcr_ro | PMU_PMCR_E);
>>  	PRINT_REGS("After 1st loop");
>>  
>>  	write_sysreg_s(0x0, PMCNTENSET_EL0);
>>  	write_regn_el0(pmevtyper, 1, CPU_CYCLES | PMEVTYPER_EXCLUDE_EL0);
>>  	write_sysreg_s(0x3, PMCNTENSET_EL0);
>>  
>> -	mem_access_loop(addr, 20, pmu.pmcr_ro | PMU_PMCR_E);
>> +	mem_access_loop(addr, COUNT, pmu.pmcr_ro | PMU_PMCR_E);
>>  	PRINT_REGS("After 2d loop");
>>  	report(read_sysreg(pmovsclr_el0) == 1,
>>  		"overflow is expected on counter 0");
>> -- 
>> 2.38.1
>>
>>


  reply	other threads:[~2023-04-24 20:09 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-15 11:07 [kvm-unit-tests PATCH 0/6] arm: pmu: Fix random failures of pmu-chain-promotion Eric Auger
2023-03-15 11:07 ` [kvm-unit-tests PATCH 1/6] arm: pmu: pmu-chain-promotion: Improve debug messages Eric Auger
2023-04-21  9:25   ` Alexandru Elisei
2023-04-24 20:09     ` Eric Auger
2023-03-15 11:07 ` [kvm-unit-tests PATCH 2/6] arm: pmu: pmu-chain-promotion: Introduce defines for count and margin values Eric Auger
2023-04-21  9:55   ` Alexandru Elisei
2023-04-24 20:09     ` Eric Auger [this message]
2023-03-15 11:07 ` [kvm-unit-tests PATCH 3/6] arm: pmu: Add extra DSB barriers in the mem_access loop Eric Auger
2023-04-21 10:25   ` Alexandru Elisei
2023-04-24 20:11     ` Eric Auger
2023-04-25 13:00       ` Alexandru Elisei
2023-05-31 20:14         ` Eric Auger
2023-03-15 11:07 ` [kvm-unit-tests PATCH 4/6] arm: pmu: Fix chain counter enable/disable sequences Eric Auger
2023-04-21 10:52   ` Alexandru Elisei
2023-04-21 11:24     ` Marc Zyngier
2023-05-31 20:15     ` Eric Auger
2023-03-15 11:07 ` [kvm-unit-tests PATCH 5/6] arm: pmu: Add pmu-memaccess-reliability test Eric Auger
2023-04-21 11:13   ` Alexandru Elisei
2023-05-31 20:15     ` Eric Auger
2023-03-15 11:07 ` [kvm-unit-tests PATCH 6/6] arm: pmu-chain-promotion: Increase the count and margin values Eric Auger
2023-04-04  6:23 ` [kvm-unit-tests PATCH 0/6] arm: pmu: Fix random failures of pmu-chain-promotion Eric Auger
2023-04-04 12:47   ` Andrew Jones
2023-04-12  7:34     ` Andrew Jones
2023-04-12  8:55       ` Alexandru Elisei
2023-04-12  8:47     ` Mark Rutland
2023-04-19  7:32       ` Eric Auger
2023-04-19  9:39         ` Alexandru Elisei
2023-04-21  8:11           ` Eric Auger

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