From: Oliver Upton <oliver.upton@linux.dev>
To: Marc Zyngier <maz@kernel.org>
Cc: kvmarm@lists.linux.dev, kvm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Zenghui Yu <yuzenghui@huawei.com>,
Ricardo Koller <ricarkol@google.com>,
Simon Veith <sveith@amazon.de>,
Reiji Watanabe <reijiw@google.com>,
Colton Lewis <coltonlewis@google.com>,
Joey Gouly <joey.gouly@arm.com>,
dwmw2@infradead.org
Subject: Re: [PATCH v3 05/18] KVM: arm64: timers: Allow physical offset without CNTPOFF_EL2
Date: Thu, 30 Mar 2023 06:42:47 +0000 [thread overview]
Message-ID: <ZCUvZ9yhfRSKRb3n@linux.dev> (raw)
In-Reply-To: <20230324144704.4193635-6-maz@kernel.org>
Hey Marc,
On Fri, Mar 24, 2023 at 02:46:51PM +0000, Marc Zyngier wrote:
> CNTPOFF_EL2 is awesome, but it is mostly vapourware, and no publicly
> available implementation has it. So for the common mortals, let's
> implement the emulated version of this thing.
>
> It means trapping accesses to the physical counter and timer, and
> emulate some of it as necessary.
>
> As for CNTPOFF_EL2, nobody sets the offset yet.
Did you consider implementing a 'fast' exit handler for counter reads?
When I took a stab at this a long time ago I had something similar [*].
Since physical counter emulation is going to effectively be used by all
systems out there right now it might be worth giving the best emulation
implementation we can.
[*]: https://lore.kernel.org/kvmarm/20210916181510.963449-9-oupton@google.com/
--
Thanks,
Oliver
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next prev parent reply other threads:[~2023-03-30 6:43 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-24 14:46 [PATCH v3 00/18] KVM: arm64: Rework timer offsetting for fun and profit Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 01/18] KVM: arm64: timers: Use a per-vcpu, per-timer accumulator for fractional ns Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 02/18] arm64: Add CNTPOFF_EL2 register definition Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 03/18] arm64: Add HAS_ECV_CNTPOFF capability Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 04/18] KVM: arm64: timers: Use CNTPOFF_EL2 to offset the physical timer Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 05/18] KVM: arm64: timers: Allow physical offset without CNTPOFF_EL2 Marc Zyngier
2023-03-30 6:42 ` Oliver Upton [this message]
2023-03-30 10:09 ` Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 06/18] KVM: arm64: Expose {un,}lock_all_vcpus() to the rest of KVM Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 07/18] KVM: arm64: timers: Allow userspace to set the global counter offset Marc Zyngier
2023-03-30 6:26 ` Oliver Upton
2023-03-30 10:15 ` Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 08/18] KVM: arm64: timers: Allow save/restoring of the physical timer Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 09/18] KVM: arm64: timers: Rationalise per-vcpu timer init Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 10/18] KVM: arm64: timers: Abstract per-timer IRQ access Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 11/18] KVM: arm64: timers: Move the timer IRQs into arch_timer_vm_data Marc Zyngier
2023-03-30 7:02 ` Oliver Upton
2023-03-30 10:19 ` Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 12/18] KVM: arm64: Abstract the number of valid timers per vcpu Marc Zyngier
2023-03-24 14:46 ` [PATCH v3 13/18] KVM: arm64: Document KVM_ARM_SET_CNT_OFFSETS and co Marc Zyngier
2023-03-24 14:47 ` [PATCH v3 14/18] KVM: arm64: nv: timers: Add a per-timer, per-vcpu offset Marc Zyngier
2023-03-24 14:47 ` [PATCH v3 15/18] KVM: arm64: nv: timers: Support hyp timer emulation Marc Zyngier
2023-03-24 14:47 ` [PATCH v3 16/18] KVM: arm64: selftests: Add physical timer registers to the sysreg list Marc Zyngier
2023-03-24 14:47 ` [PATCH v3 17/18] KVM: arm64: selftests: Deal with spurious timer interrupts Marc Zyngier
2023-03-24 14:47 ` [PATCH v3 18/18] KVM: arm64: selftests: Augment existing timer test to handle variable offset Marc Zyngier
2023-03-29 5:41 ` [PATCH v3 00/18] KVM: arm64: Rework timer offsetting for fun and profit Veith, Simon
2023-03-30 17:46 ` Marc Zyngier
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