linux-kernel - Re: [PATCH] Xen/PCI: correct notifier used for device removal

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Date:	Mon, 01 Feb 2016 05:16:27 -0700
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"David Vrabel" <david.vrabel@...rix.com>
Cc:	"xen-devel" <xen-devel@...ts.xenproject.org>,
	"Boris Ostrovsky" <boris.ostrovsky@...cle.com>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Xen/PCI: correct notifier used for device removal

>>> On 01.02.16 at 13:01, <david.vrabel@...rix.com> wrote:
> On 01/02/16 11:58, Jan Beulich wrote:
>> Commit 599bad38cf added BUS_NOTIFY_REMOVED_DEVICE in order to allow
>> avoiding removal of IOMMU mappings before the driver actually got
>> unbound from the device. Naturally we should be using this too.
> 
> Because otherwise...?  What happens if we don't make this change?
> 
> Removing IOMMU mappings for a device when the driver is still bound to
> the device looks wrong to me. Surely the device is still active and may
> still be performing DMA at this point?

Exactly - you answered your own question (as does the commit
referred to).

Jan