linux-kernel - Re: [PATCH] arm64: perf: Don't disgard upper 32 bits from PMCEID0/1 registers

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Message-ID: <5dc379a0-9068-8bec-1f28-afa7cb557c32@os.amperecomputing.com>
Date:   Thu, 26 Oct 2023 18:16:41 -0700 (PDT)
From:   Ilkka Koskinen <ilkka@...amperecomputing.com>
To:     Marc Zyngier <maz@...nel.org>
cc:     Ilkka Koskinen <ilkka@...amperecomputing.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Zaid Al-Bassam <zalbassam@...gle.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: perf: Don't disgard upper 32 bits from PMCEID0/1
 registers


Hi Marc,

On Thu, 26 Oct 2023, Marc Zyngier wrote:
> On Wed, 25 Oct 2023 21:08:15 +0100,
> Ilkka Koskinen <ilkka@...amperecomputing.com> wrote:
>>
>> The upper 32 bits of PMCEID[n] registers are used to describe whether
>> architectural and microarchitectural events in range 0x4000-0x401f
>> exist. Due to disgarding the bits, the driver made the events invisible,
>> even if they existed.
>>
>> Fixes: df29ddf4f04b ("arm64: perf: Abstract system register accesses away")
>> Reported-by: Carl Worth <carl@...amperecomputing.com>
>> Signed-off-by: Ilkka Koskinen <ilkka@...amperecomputing.com>
>> ---
>>  arch/arm64/include/asm/arm_pmuv3.h | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/arm_pmuv3.h b/arch/arm64/include/asm/arm_pmuv3.h
>> index 18dc2fb3d7b7..3e92b7cb57a4 100644
>> --- a/arch/arm64/include/asm/arm_pmuv3.h
>> +++ b/arch/arm64/include/asm/arm_pmuv3.h
>> @@ -126,12 +126,12 @@ static inline void write_pmuserenr(u32 val)
>>  	write_sysreg(val, pmuserenr_el0);
>>  }
>>
>> -static inline u32 read_pmceid0(void)
>> +static inline u64 read_pmceid0(void)
>>  {
>>  	return read_sysreg(pmceid0_el0);
>>  }
>>
>> -static inline u32 read_pmceid1(void)
>> +static inline u64 read_pmceid1(void)
>>  {
>>  	return read_sysreg(pmceid1_el0);
>>  }
>
> This is necessary, but not sufficient. You also need to update the
> corresponding 32bit accessors to match this behaviour. Something along
> the lines of the patch below
>
> 	M.

Thanks! I'll add your code to the second version.

Cheers, Ilkka


>
> diff --git a/arch/arm/include/asm/arm_pmuv3.h b/arch/arm/include/asm/arm_pmuv3.h
> index 72529f5e2bed..90841cb7ce43 100644
> --- a/arch/arm/include/asm/arm_pmuv3.h
> +++ b/arch/arm/include/asm/arm_pmuv3.h
> @@ -23,6 +23,8 @@
> #define PMUSERENR		__ACCESS_CP15(c9,  0, c14, 0)
> #define PMINTENSET		__ACCESS_CP15(c9,  0, c14, 1)
> #define PMINTENCLR		__ACCESS_CP15(c9,  0, c14, 2)
> +#define PMCEID2			__ACCESS_CP15(c9,  0, c14, 4)
> +#define PMCEID3			__ACCESS_CP15(c9,  0, c14, 5)
> #define PMMIR			__ACCESS_CP15(c9,  0, c14, 6)
> #define PMCCFILTR		__ACCESS_CP15(c14, 0, c15, 7)
>
> @@ -205,16 +207,6 @@ static inline void write_pmuserenr(u32 val)
> 	write_sysreg(val, PMUSERENR);
> }
>
> -static inline u32 read_pmceid0(void)
> -{
> -	return read_sysreg(PMCEID0);
> -}
> -
> -static inline u32 read_pmceid1(void)
> -{
> -	return read_sysreg(PMCEID1);
> -}
> -
> static inline void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr) {}
> static inline void kvm_clr_pmu_events(u32 clr) {}
> static inline bool kvm_pmu_counter_deferred(struct perf_event_attr *attr)
> @@ -231,6 +223,7 @@ static inline void kvm_vcpu_pmu_resync_el0(void) {}
>
> /* PMU Version in DFR Register */
> #define ARMV8_PMU_DFR_VER_NI        0
> +#define ARMV8_PMU_DFR_VER_V3P1      0x4
> #define ARMV8_PMU_DFR_VER_V3P4      0x5
> #define ARMV8_PMU_DFR_VER_V3P5      0x6
> #define ARMV8_PMU_DFR_VER_IMP_DEF   0xF
> @@ -251,4 +244,24 @@ static inline bool is_pmuv3p5(int pmuver)
> 	return pmuver >= ARMV8_PMU_DFR_VER_V3P5;
> }
>
> +static inline u64 read_pmceid0(void)
> +{
> +	u64 val = read_sysreg(PMCEID0);
> +
> +	if (read_pmuver() >= ARMV8_PMU_DFR_VER_V3P1)
> +		val |= (u64)read_sysreg(PMCEID2) << 32;
> +
> +	return val;
> +}
> +
> +static inline u64 read_pmceid1(void)
> +{
> +	u64 val = read_sysreg(PMCEID1);
> +
> +	if (read_pmuver() >= ARMV8_PMU_DFR_VER_V3P1)
> +		val |= (u64)read_sysreg(PMCEID3) << 32;
> +
> +	return val;
> +}
> +
> #endif
>
> -- 
> Without deviation from the norm, progress is not possible.
>