[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH 07/13] usb: Convert usb_packet_{map, unmap} to u

From: Benjamin Herrenschmidt
Subject: Re: [Qemu-devel] [PATCH 07/13] usb: Convert usb_packet_{map, unmap} to universal DMA helpers
Date: Wed, 20 Jun 2012 13:52:12 +1000

On Wed, 2012-06-20 at 13:14 +1000, David Gibson wrote:
> So, in fact the original comment is a bit out of date.  With the
> current version of this series, then a guest attempt to invalidate
> will be delayed until the unmap occurs. 

No, this code was dropped, including the tracking of the maps, following
comments from Anthony and others. The API for providing a cancel
callback is still there but nothing will call it unless the backend does
its own tracking and decides to do so.

As it is, the race exist but:

 - It will only hurt the guest

 - And only for a very buggy guest

So the worst case is that it hurts something like kdump.

I plan to re-introduce some of the mechanisms for cancellation
eventually, but we agreed that it wasn't going to be a show stopper and
that we could work on getting that sorted in a second phase. I'm looking
at a more efficient way to deal with the tracking of the maps as well
since some devices uses them often.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]