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Re: [Xen-devel] [PATCH 0 of 4] Add commands to automatically prep devices for pass-through

Hello Ian,

Thursday, May 10, 2012, 12:38:40 PM, you wrote:

> On Thu, 2012-05-10 at 11:17 +0100, George Dunlap wrote:
>> On Wed, May 9, 2012 at 2:45 PM, George Dunlap
>> <george.dunlap@xxxxxxxxxxxxx> wrote:
>> > On 09/05/12 12:59, Ian Campbell wrote:
>> >>
>> >> Right, however it is strictly speaking a new feature which is not
>> >> mentioned on the TODO list and has not previously been posted (AFAIK,
>> >> please correct me if not) and we are currently supposed to be in feature
>> >> freeze (and have been for several weeks, if not a month).
>> >>
>> >> IIRC this functionality was mooted when the pci permissive patch was
>> >> being done as something which would be a 4.3 feature.
>> >> We need to decide if we want to make an exception for this new feature
>> >> or not. Although I'm sure this feature is very nice and handy, we've
>> >> lived without it for years and people seem to be able to use the
>> >> existing scheme.
>> And, I realize that at some point all of the deadlines are going to be
>> arbitrary; but I have always felt this is important enough to get an
>> exception.  I consider having to muck about with sysfs to be basically
>> a UI bug that really needs fixing.  I have a lot of other things that
>> I would like to get done for the 4.2 release; but I thought this was
>> important enough to get priority (above the PoD patch series, for
>> instance).  NB I'm not saying that you should accept it because I
>> worked on it; I only bring it up to demonstrate how important I think
>> the feature is.

> OK, given that the code is basically self contained and shouldn't effect
> anything unless a user "opts-in" to using it I think you've convinced
> me. Lets take this (I'll review the actual patches shortly).

> BTW, IMHO it is preferable for actual deployments to use the kernel
> command line options to hide devices rather than either this feature or
> sysfs.

> Fully hiding the device from dom0 drivers generally seems like it is
> always better. That way the first driver to try and touch the hardware
> is the one inside the domU. This avoids issues with dom0 drivers setting
> stuff up but not tearing it down in a way that domU can cope with and
> makes the use of hardware which doesn't support FLR more reliable etc.

Haven't checked it (haven't got the time right now) but:
Is using wildcards in the BDF's on the commandline supported already (like the 
ones supported in the config files for domains)

I tend to have quite long commandlines to hide a pci-e card with 8 functions 
(needed to specify 8 BDF's seperatly) for pci passthrough, would be nice if one 
could just specify 09:00.* for example.

> Ian.

Best regards,
 Sander                            mailto:linux@xxxxxxxxxxxxxx

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