Re: [kvm-unit-tests PATCH v3 3/3] arm: pmu: Check for overflow in the low counter in chained counters tests

[Oliver Upton <oliver.upton@linux.dev>]

On Thu, Aug 04, 2022 at 05:41:39PM -0700, Ricardo Koller wrote:
> A chained event overflowing on the low counter can set the overflow flag
> in PMOVS.  KVM does not set it, but real HW and the fast-model seem to.
> Moreover, the AArch64.IncrementEventCounter() pseudocode in the ARM ARM
> (DDI 0487H.a, J1.1.1 "aarch64/debug") also sets the PMOVS bit on
> overflow.
> 
> The pmu chain tests fail on bare metal when checking the overflow flag
> of the low counter _not_ being set on overflow.  Fix by checking for
> overflow. Note that this test fails in KVM without the respective fix.
> 

It'd be good to link out to the respective KVM fix, either by commit or
lore link if this patch lands before the kernel patches:

Link: http://lore.kernel.org/r/20220805135813.2102034-1-maz@kernel.org

--
Thanks,
Oliver

> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Ricardo Koller <ricarkol@google.com>
> ---
>  arm/pmu.c | 33 ++++++++++++++++++---------------
>  1 file changed, 18 insertions(+), 15 deletions(-)
> 
> diff --git a/arm/pmu.c b/arm/pmu.c
> index 12e7d84e..0a7e12f8 100644
> --- a/arm/pmu.c
> +++ b/arm/pmu.c
> @@ -583,7 +583,7 @@ static void test_chained_counters(void)
>  	precise_instrs_loop(22, pmu.pmcr_ro | PMU_PMCR_E);
>  
>  	report(read_regn_el0(pmevcntr, 1) == 1, "CHAIN counter #1 incremented");
> -	report(!read_sysreg(pmovsclr_el0), "no overflow recorded for chained incr #1");
> +	report(read_sysreg(pmovsclr_el0) == 0x1, "overflow recorded for chained incr #1");
>  
>  	/* test 64b overflow */
>  
> @@ -595,7 +595,7 @@ static void test_chained_counters(void)
>  	precise_instrs_loop(22, pmu.pmcr_ro | PMU_PMCR_E);
>  	report_info("overflow reg = 0x%lx", read_sysreg(pmovsclr_el0));
>  	report(read_regn_el0(pmevcntr, 1) == 2, "CHAIN counter #1 set to 2");
> -	report(!read_sysreg(pmovsclr_el0), "no overflow recorded for chained incr #2");
> +	report(read_sysreg(pmovsclr_el0) == 0x1, "overflow recorded for chained incr #2");
>  
>  	write_regn_el0(pmevcntr, 0, PRE_OVERFLOW);
>  	write_regn_el0(pmevcntr, 1, ALL_SET);
> @@ -603,7 +603,7 @@ static void test_chained_counters(void)
>  	precise_instrs_loop(22, pmu.pmcr_ro | PMU_PMCR_E);
>  	report_info("overflow reg = 0x%lx", read_sysreg(pmovsclr_el0));
>  	report(!read_regn_el0(pmevcntr, 1), "CHAIN counter #1 wrapped");
> -	report(read_sysreg(pmovsclr_el0) == 0x2, "overflow on chain counter");
> +	report(read_sysreg(pmovsclr_el0) == 0x3, "overflow on even and odd counters");
>  }
>  
>  static void test_chained_sw_incr(void)
> @@ -629,8 +629,9 @@ static void test_chained_sw_incr(void)
>  		write_sysreg(0x1, pmswinc_el0);
>  
>  	isb();
> -	report(!read_sysreg(pmovsclr_el0) && (read_regn_el0(pmevcntr, 1) == 1),
> -		"no overflow and chain counter incremented after 100 SW_INCR/CHAIN");
> +	report((read_sysreg(pmovsclr_el0) == 0x1) &&
> +		(read_regn_el0(pmevcntr, 1) == 1),
> +		"overflow and chain counter incremented after 100 SW_INCR/CHAIN");
>  	report_info("overflow=0x%lx, #0=%ld #1=%ld", read_sysreg(pmovsclr_el0),
>  		    read_regn_el0(pmevcntr, 0), read_regn_el0(pmevcntr, 1));
>  
> @@ -648,10 +649,10 @@ static void test_chained_sw_incr(void)
>  		write_sysreg(0x1, pmswinc_el0);
>  
>  	isb();
> -	report((read_sysreg(pmovsclr_el0) == 0x2) &&
> +	report((read_sysreg(pmovsclr_el0) == 0x3) &&
>  		(read_regn_el0(pmevcntr, 1) == 0) &&
>  		(read_regn_el0(pmevcntr, 0) == 84),
> -		"overflow on chain counter and expected values after 100 SW_INCR/CHAIN");
> +		"expected overflows and values after 100 SW_INCR/CHAIN");
>  	report_info("overflow=0x%lx, #0=%ld #1=%ld", read_sysreg(pmovsclr_el0),
>  		    read_regn_el0(pmevcntr, 0), read_regn_el0(pmevcntr, 1));
>  }
> @@ -731,8 +732,9 @@ static void test_chain_promotion(void)
>  	report_info("MEM_ACCESS counter #0 has value 0x%lx",
>  		    read_regn_el0(pmevcntr, 0));
>  
> -	report((read_regn_el0(pmevcntr, 1) == 1) && !read_sysreg(pmovsclr_el0),
> -		"CHAIN counter enabled: CHAIN counter was incremented and no overflow");
> +	report((read_regn_el0(pmevcntr, 1) == 1) &&
> +		(read_sysreg(pmovsclr_el0) == 0x1),
> +		"CHAIN counter enabled: CHAIN counter was incremented and overflow");
>  
>  	report_info("CHAIN counter #1 = 0x%lx, overflow=0x%lx",
>  		read_regn_el0(pmevcntr, 1), read_sysreg(pmovsclr_el0));
> @@ -759,8 +761,9 @@ static void test_chain_promotion(void)
>  	report_info("MEM_ACCESS counter #0 has value 0x%lx",
>  		    read_regn_el0(pmevcntr, 0));
>  
> -	report((read_regn_el0(pmevcntr, 1) == 1) && !read_sysreg(pmovsclr_el0),
> -		"32b->64b: CHAIN counter incremented and no overflow");
> +	report((read_regn_el0(pmevcntr, 1) == 1) &&
> +		(read_sysreg(pmovsclr_el0) == 0x1),
> +		"32b->64b: CHAIN counter incremented and overflow");
>  
>  	report_info("CHAIN counter #1 = 0x%lx, overflow=0x%lx",
>  		read_regn_el0(pmevcntr, 1), read_sysreg(pmovsclr_el0));
> @@ -868,8 +871,8 @@ static void test_overflow_interrupt(void)
>  	write_regn_el0(pmevcntr, 0, PRE_OVERFLOW);
>  	isb();
>  	mem_access_loop(addr, 200, pmu.pmcr_ro | PMU_PMCR_E);
> -	report(expect_interrupts(0),
> -		"no overflow interrupt expected on 32b boundary");
> +	report(expect_interrupts(0x1),
> +		"expect overflow interrupt on 32b boundary");
>  
>  	/* overflow on odd counter */
>  	pmu_reset_stats();
> @@ -877,8 +880,8 @@ static void test_overflow_interrupt(void)
>  	write_regn_el0(pmevcntr, 1, ALL_SET);
>  	isb();
>  	mem_access_loop(addr, 400, pmu.pmcr_ro | PMU_PMCR_E);
> -	report(expect_interrupts(0x2),
> -		"expect overflow interrupt on odd counter");
> +	report(expect_interrupts(0x3),
> +		"expect overflow interrupt on even and odd counter");
>  }
>  #endif
>  
> -- 
> 2.37.1.559.g78731f0fdb-goog
>