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Date:   Sat, 30 Mar 2019 09:56:14 +0000
Message-ID: <86wokg65z5.wl-marc.zyngier@arm.com>
From:   Marc Zyngier <marc.zyngier@arm.com>
To:     Wei Huang <wei@redhat.com>
Cc:     <linux-kernel@vger.kernel.org>, <kvmarm@lists.cs.columbia.edu>,
        <linux-arm-kernel@lists.infradead.org>, <andre.przywara@arm.com>,
        <christoffer.dall@arm.com>, <james.morse@arm.com>,
        <julien.thierry@arm.com>, <suzuki.poulose@arm.com>
Subject: Re: [PATCH 1/1] KVM: arm/arm64: arch_timer: Fix TimerValue TVAL calculation in KVM
In-Reply-To: <20190329201253.29164-1-wei@redhat.com>
References: <20190329201253.29164-1-wei@redhat.com>
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On Fri, 29 Mar 2019 20:12:53 +0000,
Wei Huang <wei@redhat.com> wrote:
> 
> Recently the generic timer test of kvm-unit-tests failed to complete
> (stalled) when a physical timer is being used. This issue is caused
> by incorrect update of CNT_CVAL when TimerValue is being accessed,
> introduced by 'Commit 84135d3d18da ("KVM: arm/arm64: consolidate arch
> timer trap handlers")'. According to Arm ARM, the read/write behavior
> of accesses to TimeValue registers is expected to be:
> 
>   * READ: TimerValue = (CompareValue – (Counter - Offset)
>   * WRITE: CompareValue = ((Counter - Offset) + Sign(TimerValue)
> 
> This patch fixes the TVAL read/write code path according to the
> specification.
> 
> Signed-off-by: Wei Huang <wei@redhat.com>

Huh... Nice catch. I guess I only ran this with a VHE host, where this
code path is unused.

Thanks,

	M.

-- 
Jazz is not dead, it just smell funny.