linux-kernel - Re: [PATCH v2] PCI/DPC: Fix shared interrupt handling

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Date:   Thu, 14 Dec 2017 08:50:23 -0700
From:   Keith Busch <keith.busch@...el.com>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     linux-pci@...r.kernel.org, bhelgaas@...gle.com,
        liudongdong3@...wei.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI/DPC: Fix shared interrupt handling

On Thu, Dec 14, 2017 at 08:20:18AM -0700, Alex Williamson wrote:
> DPC supports shared interrupts, but it plays very loosely with testing
> whether the interrupt is generated by DPC before generating spurious
> log messages, such as:
> 
>  dpc 0000:10:01.2:pcie010: DPC containment event, status:0x1f00 source:0x0000
> 
> Testing the status register for zero or -1 is not sufficient when the
> device supports the RP PIO First Error Pointer register.  Change this
> to test whether the interrupt is enabled in the control register,
> retaining the device present test, and that the status reports the
> interrupt as signaled and DPC is triggered, clearing as a spurious
> interrupt otherwise.
> 
> Additionally, since the interrupt is actually serviced by a workqueue,
> disable the interrupt in the control register until that completes or
> else we may never see it execute due to further incoming interrupts.
> A software generated DPC floods the system otherwise.
> 
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>

Thanks, looks good.

Reviewed-by: Keith Busch <keith.busch@...el.com>