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From: Marc Zyngier <maz@kernel.org>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: kernel-team@android.com, kvm@vger.kernel.org,
	Robin Murphy <robin.murphy@arm.com>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/3] KVM: arm64: Narrow PMU sysreg reset values to architectural requirements
Date: Tue, 13 Jul 2021 16:59:58 +0100	[thread overview]
Message-ID: <87mtqq6w75.wl-maz@kernel.org> (raw)
In-Reply-To: <20210713143949.GJ22278@shell.armlinux.org.uk>

On Tue, 13 Jul 2021 15:39:49 +0100,
"Russell King (Oracle)" <linux@armlinux.org.uk> wrote:
> 
> On Tue, Jul 13, 2021 at 02:58:58PM +0100, Marc Zyngier wrote:
> > +static void reset_pmu_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> > +{
> > +	u64 n, mask;
> > +
> > +	/* No PMU available, any PMU reg may UNDEF... */
> > +	if (!kvm_arm_support_pmu_v3())
> > +		return;
> > +
> > +	n = read_sysreg(pmcr_el0) >> ARMV8_PMU_PMCR_N_SHIFT;
> > +	n &= ARMV8_PMU_PMCR_N_MASK;
> > +
> > +	reset_unknown(vcpu, r);
> > +
> > +	mask = BIT(ARMV8_PMU_CYCLE_IDX);
> > +	if (n)
> > +		mask |= GENMASK(n - 1, 0);
> > +
> > +	__vcpu_sys_reg(vcpu, r->reg) &= mask;
> 
> Would this read more logically to structure it as:
> 
> 	mask = BIT(ARMV8_PMU_CYCLE_IDX);
> 
> 	n = read_sysreg(pmcr_el0) >> ARMV8_PMU_PMCR_N_SHIFT;
> 	n &= ARMV8_PMU_PMCR_N_MASK;
> 	if (n)
> 		mask |= GENMASK(n - 1, 0);
> 
> 	reset_unknown(vcpu, r);
> 	__vcpu_sys_reg(vcpu, r->reg) &= mask;
> 
> ?

Yup, that's nicer. Amended locally.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.
_______________________________________________
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: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	kvmarm@lists.cs.columbia.edu, James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Alexandre Chartre <alexandre.chartre@oracle.com>,
	Robin Murphy <robin.murphy@arm.com>,
	kernel-team@android.com
Subject: Re: [PATCH 1/3] KVM: arm64: Narrow PMU sysreg reset values to architectural requirements
Date: Tue, 13 Jul 2021 16:59:58 +0100	[thread overview]
Message-ID: <87mtqq6w75.wl-maz@kernel.org> (raw)
In-Reply-To: <20210713143949.GJ22278@shell.armlinux.org.uk>

On Tue, 13 Jul 2021 15:39:49 +0100,
"Russell King (Oracle)" <linux@armlinux.org.uk> wrote:
> 
> On Tue, Jul 13, 2021 at 02:58:58PM +0100, Marc Zyngier wrote:
> > +static void reset_pmu_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> > +{
> > +	u64 n, mask;
> > +
> > +	/* No PMU available, any PMU reg may UNDEF... */
> > +	if (!kvm_arm_support_pmu_v3())
> > +		return;
> > +
> > +	n = read_sysreg(pmcr_el0) >> ARMV8_PMU_PMCR_N_SHIFT;
> > +	n &= ARMV8_PMU_PMCR_N_MASK;
> > +
> > +	reset_unknown(vcpu, r);
> > +
> > +	mask = BIT(ARMV8_PMU_CYCLE_IDX);
> > +	if (n)
> > +		mask |= GENMASK(n - 1, 0);
> > +
> > +	__vcpu_sys_reg(vcpu, r->reg) &= mask;
> 
> Would this read more logically to structure it as:
> 
> 	mask = BIT(ARMV8_PMU_CYCLE_IDX);
> 
> 	n = read_sysreg(pmcr_el0) >> ARMV8_PMU_PMCR_N_SHIFT;
> 	n &= ARMV8_PMU_PMCR_N_MASK;
> 	if (n)
> 		mask |= GENMASK(n - 1, 0);
> 
> 	reset_unknown(vcpu, r);
> 	__vcpu_sys_reg(vcpu, r->reg) &= mask;
> 
> ?

Yup, that's nicer. Amended locally.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

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

WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	kvmarm@lists.cs.columbia.edu, James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Alexandre Chartre <alexandre.chartre@oracle.com>,
	Robin Murphy <robin.murphy@arm.com>,
	kernel-team@android.com
Subject: Re: [PATCH 1/3] KVM: arm64: Narrow PMU sysreg reset values to architectural requirements
Date: Tue, 13 Jul 2021 16:59:58 +0100	[thread overview]
Message-ID: <87mtqq6w75.wl-maz@kernel.org> (raw)
In-Reply-To: <20210713143949.GJ22278@shell.armlinux.org.uk>

On Tue, 13 Jul 2021 15:39:49 +0100,
"Russell King (Oracle)" <linux@armlinux.org.uk> wrote:
> 
> On Tue, Jul 13, 2021 at 02:58:58PM +0100, Marc Zyngier wrote:
> > +static void reset_pmu_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> > +{
> > +	u64 n, mask;
> > +
> > +	/* No PMU available, any PMU reg may UNDEF... */
> > +	if (!kvm_arm_support_pmu_v3())
> > +		return;
> > +
> > +	n = read_sysreg(pmcr_el0) >> ARMV8_PMU_PMCR_N_SHIFT;
> > +	n &= ARMV8_PMU_PMCR_N_MASK;
> > +
> > +	reset_unknown(vcpu, r);
> > +
> > +	mask = BIT(ARMV8_PMU_CYCLE_IDX);
> > +	if (n)
> > +		mask |= GENMASK(n - 1, 0);
> > +
> > +	__vcpu_sys_reg(vcpu, r->reg) &= mask;
> 
> Would this read more logically to structure it as:
> 
> 	mask = BIT(ARMV8_PMU_CYCLE_IDX);
> 
> 	n = read_sysreg(pmcr_el0) >> ARMV8_PMU_PMCR_N_SHIFT;
> 	n &= ARMV8_PMU_PMCR_N_MASK;
> 	if (n)
> 		mask |= GENMASK(n - 1, 0);
> 
> 	reset_unknown(vcpu, r);
> 	__vcpu_sys_reg(vcpu, r->reg) &= mask;
> 
> ?

Yup, that's nicer. Amended locally.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

  reply	other threads:[~2021-07-13 16:00 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-13 13:58 [PATCH 0/3] kvm-arm64: Fix PMU reset values (and more) Marc Zyngier
2021-07-13 13:58 ` Marc Zyngier
2021-07-13 13:58 ` Marc Zyngier
2021-07-13 13:58 ` [PATCH 1/3] KVM: arm64: Narrow PMU sysreg reset values to architectural requirements Marc Zyngier
2021-07-13 13:58   ` Marc Zyngier
2021-07-13 13:58   ` Marc Zyngier
2021-07-13 14:39   ` Russell King (Oracle)
2021-07-13 14:39     ` Russell King (Oracle)
2021-07-13 14:39     ` Russell King (Oracle)
2021-07-13 15:59     ` Marc Zyngier [this message]
2021-07-13 15:59       ` Marc Zyngier
2021-07-13 15:59       ` Marc Zyngier
2021-07-13 16:15       ` Russell King (Oracle)
2021-07-13 16:15         ` Russell King (Oracle)
2021-07-13 16:15         ` Russell King (Oracle)
2021-07-14 15:48   ` Alexandru Elisei
2021-07-14 15:48     ` Alexandru Elisei
2021-07-14 15:48     ` Alexandru Elisei
2021-07-15 11:11     ` Marc Zyngier
2021-07-15 11:11       ` Marc Zyngier
2021-07-15 11:11       ` Marc Zyngier
2021-07-15 11:51       ` Robin Murphy
2021-07-15 11:51         ` Robin Murphy
2021-07-15 11:51         ` Robin Murphy
2021-07-15 12:25         ` Marc Zyngier
2021-07-15 12:25           ` Marc Zyngier
2021-07-15 12:25           ` Marc Zyngier
2021-07-13 13:58 ` [PATCH 2/3] KVM: arm64: Drop unnecessary masking of PMU registers Marc Zyngier
2021-07-13 13:58   ` Marc Zyngier
2021-07-13 13:58   ` Marc Zyngier
2021-07-14 16:12   ` Alexandru Elisei
2021-07-14 16:12     ` Alexandru Elisei
2021-07-14 16:12     ` Alexandru Elisei
2021-07-13 13:59 ` [PATCH 3/3] KVM: arm64: Disabling disabled PMU counters wastes a lot of time Marc Zyngier
2021-07-13 13:59   ` Marc Zyngier
2021-07-13 13:59   ` Marc Zyngier
2021-07-14 16:18   ` Alexandru Elisei
2021-07-14 16:18     ` Alexandru Elisei
2021-07-14 16:18     ` Alexandru Elisei
2021-07-15  8:34 ` [PATCH 0/3] kvm-arm64: Fix PMU reset values (and more) Alexandre Chartre
2021-07-15  8:34   ` Alexandre Chartre
2021-07-15  8:34   ` Alexandre Chartre

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