linux-kernel - Re: [Patch V2] ioatdma: Ignore IOAT devices under hotplug-capable PCI host bridge

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Message-ID: <20150716125930.GP5086@localhost>
Date:	Thu, 16 Jul 2015 18:29:30 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Jiang Liu <jiang.liu@...ux.intel.com>
Cc:	Dave Jiang <dave.jiang@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Tony Luck <tony.luck@...el.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org
Subject: Re: [Patch V2] ioatdma: Ignore IOAT devices under hotplug-capable
 PCI host bridge

On Wed, Jul 08, 2015 at 03:41:42PM +0800, Jiang Liu wrote:
> The dmaengine core assumes that async DMA devices will only be removed
> when they not used anymore, or it assumes dma_async_device_unregister()
> will only be called by dma driver exit routines. But this assumption is
> not true for the IOAT driver, which calls dma_async_device_unregister()
> from ioat_remove(). So current IOAT driver doesn't support device
> hot-removal because it may cause system crash to hot-remove an inuse
> IOAT device.
> 
> To support CPU socket hot-removal, all PCI devices, including IOAT
> devices embedded in the socket, will be hot-removed. The idea solution
> is to enhance the dmaengine core and IOAT driver to support hot-removal,
> but that's too hard.
> 
> This patch implements a hack to disable IOAT devices under hotplug-capable
> CPU socket so it won't break socket hot-removal.

Applied now, please ensure you use the right subsystem name

-- 
~Vinod

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