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Subject: Re: [PATCH v3 10/10] clocksource/drivers/hyper-v: Move handling of
 STIMER0 interrupts
To:     Michael Kelley <mikelley@microsoft.com>, sthemmin@microsoft.com,
        kys@microsoft.com, wei.liu@kernel.org, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, hpa@zytor.com, arnd@arndb.de,
        linux-hyperv@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        linux-arch@vger.kernel.org
References: <1614721102-2241-1-git-send-email-mikelley@microsoft.com>
 <1614721102-2241-11-git-send-email-mikelley@microsoft.com>
From:   Daniel Lezcano <daniel.lezcano@linaro.org>
Message-ID: <5495b52c-e619-90c4-0c4f-fdbde9e1ce58@linaro.org>
Date:   Tue, 2 Mar 2021 23:18:40 +0100
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On 02/03/2021 22:38, Michael Kelley wrote:
> STIMER0 interrupts are most naturally modeled as per-cpu IRQs. But
> because x86/x64 doesn't have per-cpu IRQs, the core STIMER0 interrupt
> handling machinery is done in code under arch/x86 and Linux IRQs are
> not used. Adding support for ARM64 means adding equivalent code
> using per-cpu IRQs under arch/arm64.
> 
> A better model is to treat per-cpu IRQs as the normal path (which it is
> for modern architectures), and the x86/x64 path as the exception. Do this
> by incorporating standard Linux per-cpu IRQ allocation into the main
> SITMER0 driver code, and bypass it in the x86/x64 exception case. For
> x86/x64, special case code is retained under arch/x86, but no STIMER0
> interrupt handling code is needed under arch/arm64.
> 
> No functional change.
> 
> Signed-off-by: Michael Kelley <mikelley@microsoft.com>

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

[ ... ]

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