linux-kernel - Re: [PATCH] x86/hpet: Cure interface abuse in the resume path

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Date:   Tue, 1 Aug 2017 10:30:28 +0300
From:   Tomi Sarvela <tomi.p.sarvela@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        Martin Peres <martin.peres@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Marc Zyngier <marc.zyngier@....com>, jeffy.chen@...k-chips.com
Subject: Re: [PATCH] x86/hpet: Cure interface abuse in the resume path

On 31/07/17 23:07, Thomas Gleixner wrote:
> The HPET resume path abuses irq_domain_[de]activate_irq() to restore the
> MSI message in the HPET chip for the boot CPU on resume and it relies on an
> implementation detail of the interrupt core code, which magically makes the
> HPET unmask call invoked via a irq_disable/enable pair. This worked as long
> as the irq code did unconditionally invoke the unmask() callback. With the
> recent changes which keep track of the masked state to avoid expensive
> hardware access, this does not longer work. As a consequence the HPET timer
> interrupts are not unmasked which breaks resume as the boot CPU waits
> forever that a timer interrupt arrives.
> 
> Make the restore of the MSI message explicit and invoke the unmask()
> function directly. While at it get rid of the pointless affinity setting as
> nothing can change the affinity of the interrupt and the vector across
> suspend/resume. The restore of the MSI message reestablishes the previous
> affinity setting which is the correct one.
> 
> Fixes: bf22ff45bed6 ("genirq: Avoid unnecessary low level irq function calls")
> Reported-by: Martin Peres <martin.peres@...ux.intel.com>
> Reported-by: Tomi Sarvela <tomi.p.sarvela@...el.com>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: jeffy.chen@...k-chips.com
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: Peter Ziljstra <peterz@...radead.org>
> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>

Tested-by: Tomi Sarvela <tomi.p.sarvela@...el.com>

Tested only on the regressed Eagle Lake testhost. This patch fixes the 
suspend/resume issue.

Tomi
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