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

From "Jan Beulich" <JBeulich@suse.com>
Newsgroups linux.kernel
Subject Re: [PATCH] Xen/PCI: correct notifier used for device removal
Date 2016-02-01 14:10 +0100
Message-ID <qXmoX-3eN-51@gated-at.bofh.it> (permalink)
References <qXljc-25A-19@gated-at.bofh.it> <qXlsT-2sn-21@gated-at.bofh.it> <qXlCy-2xe-11@gated-at.bofh.it> <qXmoX-3eN-53@gated-at.bofh.it>
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>>> On 01.02.16 at 14:03, <david.vrabel@citrix.com> wrote:
> On 01/02/16 12:16, Jan Beulich wrote:
>>>>> On 01.02.16 at 13:01, <david.vrabel@citrix.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).
> 
> I misread, sorry.  I think I will reword this as:
> 
> "Commit 599bad38cf added BUS_NOTIFY_REMOVED_DEVICE to defer the removal
> of IOMMU mappings until the driver has been unbound from the device
> (i.e., until it is guaranteed that there are no outstanding DMA
> transactions).

If you want this, then I think you should add "... or IRQs".

Thanks, Jan

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Thread

[PATCH] Xen/PCI: correct notifier used for device removal "Jan Beulich" <JBeulich@suse.com> - 2016-02-01 13:00 +0100
  Re: [PATCH] Xen/PCI: correct notifier used for device removal David Vrabel <david.vrabel@citrix.com> - 2016-02-01 13:10 +0100
    Re: [PATCH] Xen/PCI: correct notifier used for device removal "Jan Beulich" <JBeulich@suse.com> - 2016-02-01 13:20 +0100
      Re: [PATCH] Xen/PCI: correct notifier used for device removal "Jan Beulich" <JBeulich@suse.com> - 2016-02-01 14:10 +0100
      Re: [PATCH] Xen/PCI: correct notifier used for device removal David Vrabel <david.vrabel@citrix.com> - 2016-02-01 14:20 +0100

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