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From: Marc Zyngier <marc.zyngier@arm.com>
To: Christoffer Dall <christoffer.dall@linaro.org>
Cc: kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	Shih-Wei Li <shihwei@cs.columbia.edu>,
	Christoffer Dall <cdall@linaro.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH v4 03/20] arm64: Use physical counter for in-kernel reads when booted in EL2
Date: Wed, 25 Oct 2017 14:43:59 +0100	[thread overview]
Message-ID: <86o9ovcpgg.fsf@arm.com> (raw)
In-Reply-To: <20171020114939.12554-4-christoffer.dall@linaro.org> (Christoffer Dall's message of "Fri, 20 Oct 2017 13:49:22 +0200")

On Fri, Oct 20 2017 at  1:49:22 pm BST, Christoffer Dall <christoffer.dall@linaro.org> wrote:
> From: Christoffer Dall <cdall@linaro.org>
>
> Using the physical counter allows KVM to retain the offset between the
> virtual and physical counter as long as it is actively running a VCPU.
>
> As soon as a VCPU is released, another thread is scheduled or we start
> running userspace applications, we reset the offset to 0, so that
> userspace accessing the virtual timer can still read the virtual counter
> and get the same view of time as the kernel.
>
> This opens up potential improvements for KVM performance, but we have to
> make a few adjustments to preserve system consistency.
>
> Currently get_cycles() is hardwired to arch_counter_get_cntvct() on
> arm64, but as we move to using the physical timer for the in-kernel
> time-keeping on systems that boot in EL2, we should use the same counter
> for get_cycles() as for other in-kernel timekeeping operations.
>
> Similarly, implementations of arch_timer_set_next_event_phys() is
> modified to use the counter specific to the timer being programmed.
>
> VHE kernels or kernels continuing to use the virtual timer are
> unaffected.
>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Christoffer Dall <cdall@linaro.org>

Acked-by: Marc Zyngier <marc.zyngier@arm.com>

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

WARNING: multiple messages have this Message-ID (diff)
From: marc.zyngier@arm.com (Marc Zyngier)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v4 03/20] arm64: Use physical counter for in-kernel reads when booted in EL2
Date: Wed, 25 Oct 2017 14:43:59 +0100	[thread overview]
Message-ID: <86o9ovcpgg.fsf@arm.com> (raw)
In-Reply-To: <20171020114939.12554-4-christoffer.dall@linaro.org> (Christoffer Dall's message of "Fri, 20 Oct 2017 13:49:22 +0200")

On Fri, Oct 20 2017 at  1:49:22 pm BST, Christoffer Dall <christoffer.dall@linaro.org> wrote:
> From: Christoffer Dall <cdall@linaro.org>
>
> Using the physical counter allows KVM to retain the offset between the
> virtual and physical counter as long as it is actively running a VCPU.
>
> As soon as a VCPU is released, another thread is scheduled or we start
> running userspace applications, we reset the offset to 0, so that
> userspace accessing the virtual timer can still read the virtual counter
> and get the same view of time as the kernel.
>
> This opens up potential improvements for KVM performance, but we have to
> make a few adjustments to preserve system consistency.
>
> Currently get_cycles() is hardwired to arch_counter_get_cntvct() on
> arm64, but as we move to using the physical timer for the in-kernel
> time-keeping on systems that boot in EL2, we should use the same counter
> for get_cycles() as for other in-kernel timekeeping operations.
>
> Similarly, implementations of arch_timer_set_next_event_phys() is
> modified to use the counter specific to the timer being programmed.
>
> VHE kernels or kernels continuing to use the virtual timer are
> unaffected.
>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Christoffer Dall <cdall@linaro.org>

Acked-by: Marc Zyngier <marc.zyngier@arm.com>

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

  reply	other threads:[~2017-10-25 13:44 UTC|newest]

Thread overview: 74+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-20 11:49 [PATCH v4 00/20] KVM: arm/arm64: Optimize arch timer register handling Christoffer Dall
2017-10-20 11:49 ` Christoffer Dall
2017-10-20 11:49 ` [PATCH v4 01/20] irqchip/gic: Deal with broken firmware exposing only 4kB of GICv2 CPU interface Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-20 11:49 ` [PATCH v4 02/20] arm64: Implement arch_counter_get_cntpct to read the physical counter Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-25 13:41   ` Marc Zyngier
2017-10-25 13:41     ` Marc Zyngier
2017-10-20 11:49 ` [PATCH v4 03/20] arm64: Use physical counter for in-kernel reads when booted in EL2 Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-25 13:43   ` Marc Zyngier [this message]
2017-10-25 13:43     ` Marc Zyngier
2017-10-20 11:49 ` [PATCH v4 04/20] KVM: arm/arm64: Guard kvm_vgic_map_is_active against !vgic_initialized Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-20 11:49 ` [PATCH v4 05/20] KVM: arm/arm64: Support calling vgic_update_irq_pending from irq context Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-25 13:45   ` Marc Zyngier
2017-10-25 13:45     ` Marc Zyngier
2017-10-20 11:49 ` [PATCH v4 06/20] KVM: arm/arm64: Check that system supports split eoi/deactivate Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-25 13:47   ` Marc Zyngier
2017-10-25 13:47     ` Marc Zyngier
2017-10-20 11:49 ` [PATCH v4 07/20] KVM: arm/arm64: Make timer_arm and timer_disarm helpers more generic Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-25 13:49   ` Marc Zyngier
2017-10-25 13:49     ` Marc Zyngier
2017-10-20 11:49 ` [PATCH v4 08/20] KVM: arm/arm64: Rename soft timer to bg_timer Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-20 11:49 ` [PATCH v4 09/20] KVM: arm/arm64: Move timer/vgic flush/sync under disabled irq Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-20 11:49 ` [PATCH v4 10/20] KVM: arm/arm64: Use separate timer for phys timer emulation Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-25 13:59   ` Marc Zyngier
2017-10-25 13:59     ` Marc Zyngier
2017-10-20 11:49 ` [PATCH v4 11/20] KVM: arm/arm64: Move timer save/restore out of the hyp code Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-20 11:49 ` [PATCH v4 12/20] genirq: Document vcpu_info usage for percpu_devid interrupts Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-20 11:56   ` Thomas Gleixner
2017-10-20 11:56     ` Thomas Gleixner
2017-10-21 14:29     ` Christoffer Dall
2017-10-21 14:29       ` Christoffer Dall
2017-10-21 14:55       ` Thomas Gleixner
2017-10-21 14:55         ` Thomas Gleixner
2017-10-21 15:30         ` Christoffer Dall
2017-10-21 15:30           ` Christoffer Dall
2017-10-20 11:49 ` [PATCH v4 13/20] KVM: arm/arm64: Set VCPU affinity for virt timer irq Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-20 11:49 ` [PATCH v4 14/20] KVM: arm/arm64: Avoid timer save/restore in vcpu entry/exit Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-25 14:36   ` Marc Zyngier
2017-10-25 14:36     ` Marc Zyngier
2017-11-16 20:30   ` Jintack Lim
2017-11-16 20:30     ` Jintack Lim
2017-11-16 20:32     ` Jintack Lim
2017-11-16 20:32       ` Jintack Lim
2017-11-20 11:15     ` Christoffer Dall
2017-11-20 11:15       ` Christoffer Dall
2017-11-20 16:32       ` Jintack Lim
2017-11-20 16:32         ` Jintack Lim
2017-10-20 11:49 ` [PATCH v4 15/20] KVM: arm/arm64: Support EL1 phys timer register access in set/get reg Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-25 14:38   ` Marc Zyngier
2017-10-25 14:38     ` Marc Zyngier
2017-10-20 11:49 ` [PATCH v4 16/20] KVM: arm/arm64: Use kvm_arm_timer_set/get_reg for guest register traps Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-20 11:49 ` [PATCH v4 17/20] KVM: arm/arm64: Move phys_timer_emulate function Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-20 11:49 ` [PATCH v4 18/20] KVM: arm/arm64: Avoid phys timer emulation in vcpu entry/exit Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-20 11:49 ` [PATCH v4 19/20] KVM: arm/arm64: Get rid of kvm_timer_flush_hwstate Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall
2017-10-20 11:49 ` [PATCH v4 20/20] KVM: arm/arm64: Rework kvm_timer_should_fire Christoffer Dall
2017-10-20 11:49   ` Christoffer Dall

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