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From: Marc Zyngier <maz@kernel.org>
To: Andrew Murray <andrew.murray@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 2/3] KVM: arm64: limit PMU version to ARMv8.4
Date: Thu, 23 Jan 2020 17:04:36 +0000	[thread overview]
Message-ID: <e59eeba41a2721e4cedb7172e714141c@kernel.org> (raw)
In-Reply-To: <20200123115852.55595-3-andrew.murray@arm.com>

On 2020-01-23 11:58, Andrew Murray wrote:
> ARMv8.5-PMU introduces 64-bit event counters, however KVM doesn't yet
> support this. Let's trap the Debug Feature Registers in order to limit
> PMUVer/PerfMon in the Debug Feature Registers to PMUv3 for ARMv8.4.
> 
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
>  arch/arm64/include/asm/sysreg.h |  5 +++++
>  arch/arm64/kvm/sys_regs.c       | 11 +++++++++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/sysreg.h 
> b/arch/arm64/include/asm/sysreg.h
> index 6e919fafb43d..d969df417f88 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -672,6 +672,11 @@
>  #define ID_AA64DFR0_TRACEVER_SHIFT	4
>  #define ID_AA64DFR0_DEBUGVER_SHIFT	0
> 
> +#define ID_DFR0_PERFMON_SHIFT		24
> +
> +#define ID_DFR0_EL1_PMUVER_8_4		5
> +#define ID_AA64DFR0_EL1_PMUVER_8_4	5
> +
>  #define ID_ISAR5_RDM_SHIFT		24
>  #define ID_ISAR5_CRC32_SHIFT		16
>  #define ID_ISAR5_SHA2_SHIFT		12
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 9f2165937f7d..028c93a88a51 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1085,6 +1085,17 @@ static u64 read_id_reg(const struct kvm_vcpu 
> *vcpu,
>  			 (0xfUL << ID_AA64ISAR1_API_SHIFT) |
>  			 (0xfUL << ID_AA64ISAR1_GPA_SHIFT) |
>  			 (0xfUL << ID_AA64ISAR1_GPI_SHIFT));
> +	} else if (id == SYS_ID_AA64DFR0_EL1) {
> +		/* Limit guests to PMUv3 for ARMv8.4 */
> +		val = cpuid_feature_cap_signed_field_width(val,
> +						ID_AA64DFR0_PMUVER_SHIFT,
> +						4, ID_AA64DFR0_EL1_PMUVER_8_4);
> +	} else if (id == SYS_ID_DFR0_EL1) {
> +		/* Limit guests to PMUv3 for ARMv8.4 */
> +		val = cpuid_feature_cap_signed_field_width(val,
> +						ID_DFR0_PERFMON_SHIFT,
> +						4, ID_DFR0_EL1_PMUVER_8_4);

I dont think this is right. Even today, we don't have support for PMMIR,
so pretending we support v8.4 is not true (the guest will get an UNDEF).
I would really stick to ARMv8.1 support here.

You could post it as a fix, to be taken right away.

         M.
-- 
Jazz is not dead. It just smells funny...
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Andrew Murray <andrew.murray@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 2/3] KVM: arm64: limit PMU version to ARMv8.4
Date: Thu, 23 Jan 2020 17:04:36 +0000	[thread overview]
Message-ID: <e59eeba41a2721e4cedb7172e714141c@kernel.org> (raw)
In-Reply-To: <20200123115852.55595-3-andrew.murray@arm.com>

On 2020-01-23 11:58, Andrew Murray wrote:
> ARMv8.5-PMU introduces 64-bit event counters, however KVM doesn't yet
> support this. Let's trap the Debug Feature Registers in order to limit
> PMUVer/PerfMon in the Debug Feature Registers to PMUv3 for ARMv8.4.
> 
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
>  arch/arm64/include/asm/sysreg.h |  5 +++++
>  arch/arm64/kvm/sys_regs.c       | 11 +++++++++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/sysreg.h 
> b/arch/arm64/include/asm/sysreg.h
> index 6e919fafb43d..d969df417f88 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -672,6 +672,11 @@
>  #define ID_AA64DFR0_TRACEVER_SHIFT	4
>  #define ID_AA64DFR0_DEBUGVER_SHIFT	0
> 
> +#define ID_DFR0_PERFMON_SHIFT		24
> +
> +#define ID_DFR0_EL1_PMUVER_8_4		5
> +#define ID_AA64DFR0_EL1_PMUVER_8_4	5
> +
>  #define ID_ISAR5_RDM_SHIFT		24
>  #define ID_ISAR5_CRC32_SHIFT		16
>  #define ID_ISAR5_SHA2_SHIFT		12
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 9f2165937f7d..028c93a88a51 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1085,6 +1085,17 @@ static u64 read_id_reg(const struct kvm_vcpu 
> *vcpu,
>  			 (0xfUL << ID_AA64ISAR1_API_SHIFT) |
>  			 (0xfUL << ID_AA64ISAR1_GPA_SHIFT) |
>  			 (0xfUL << ID_AA64ISAR1_GPI_SHIFT));
> +	} else if (id == SYS_ID_AA64DFR0_EL1) {
> +		/* Limit guests to PMUv3 for ARMv8.4 */
> +		val = cpuid_feature_cap_signed_field_width(val,
> +						ID_AA64DFR0_PMUVER_SHIFT,
> +						4, ID_AA64DFR0_EL1_PMUVER_8_4);
> +	} else if (id == SYS_ID_DFR0_EL1) {
> +		/* Limit guests to PMUv3 for ARMv8.4 */
> +		val = cpuid_feature_cap_signed_field_width(val,
> +						ID_DFR0_PERFMON_SHIFT,
> +						4, ID_DFR0_EL1_PMUVER_8_4);

I dont think this is right. Even today, we don't have support for PMMIR,
so pretending we support v8.4 is not true (the guest will get an UNDEF).
I would really stick to ARMv8.1 support here.

You could post it as a fix, to be taken right away.

         M.
-- 
Jazz is not dead. It just smells funny...

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-01-23 17:04 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-23 11:58 [PATCH v4 0/3] arm64: perf: Add support for ARMv8.5-PMU 64-bit counters Andrew Murray
2020-01-23 11:58 ` Andrew Murray
2020-01-23 11:58 ` [PATCH v4 1/3] arm64: cpufeature: Extract capped fields Andrew Murray
2020-01-23 11:58   ` Andrew Murray
2020-01-23 11:58 ` [PATCH v4 2/3] KVM: arm64: limit PMU version to ARMv8.4 Andrew Murray
2020-01-23 11:58   ` Andrew Murray
2020-01-23 17:04   ` Marc Zyngier [this message]
2020-01-23 17:04     ` Marc Zyngier
2020-01-23 11:58 ` [PATCH v4 3/3] arm64: perf: Add support for ARMv8.5-PMU 64-bit counters Andrew Murray
2020-01-23 11:58   ` Andrew Murray

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