Re: [Xen-devel] xen-pciback.hide syntax

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Friday, October 19, 2012, 9:35:24 PM, you wrote:

> On Tue, Jul 31, 2012 at 05:40:14PM +0200, Sander Eikelenboom wrote:
>> Hello Konrad,
>> 
>> Tuesday, July 31, 2012, 5:25:58 PM, you wrote:
>> 
>> > On Mon, Jul 30, 2012 at 09:47:41PM +0200, Sander Eikelenboom wrote:
>> >> Monday, July 30, 2012, 9:00:06 PM, you wrote:
>> >> 
>> >> > On Sat, May 19, 2012 at 10:46:15AM +0200, Sander Eikelenboom wrote:
>> >> >> Hi Konrad,
>> >> >> 
>> >> >> The syntax for specifying the devices for pciback to hide is 
>> >> >> "bus:device.function".
>> >> >> While thinking about cooking up a patch to be able to use a "*" 
>> >> >> wildcard for the function, i was wondering if not hiding all functions 
>> >> >> of a device is feasible at all.
>> >> >> 
>> >> >> For what I understand of PCI, function 0 is always required, so if I 
>> >> >> only hide function 0, i can't use the other functions in dom0, since 
>> >> >> those functions would require a function 0, which is hidden.
>> >> >> 
>> >> >> So would it be more logical to drop/ignore the function from the BDF, 
>> >> >> and always hide all functions from a device ?
>> >> 
>> >> > That might run afoul of the SR-IOV virtual devices. They (when loaded) 
>> >> > provide a fake
>> >> > bus:device:function, where the device is port (so if the SR-IOV card 
>> >> > has two
>> >> > jacks, you get 00 and 01), and the function is for the amount of VFs it 
>> >> > can make.
>> >> > On the Intel SR-IOV NIC with 'igbvf.max_vfs=7' I end up with 14 PCI 
>> >> > devices, where
>> >> > the function bear no resemblence to each other (and can be passed in 
>> >> > different guests).
>> >> 
>> >> > The PCI restriction I know of is if the device is behind a bridge. The 
>> >> > issue here
>> >> > is that .. well, you could pass in a different function to a different 
>> >> > guest, but
>> >> > one guest's hardware device could listen on the other guests' function. 
>> >> > It would
>> >> > require tweaking the driver to dump the contents of some registers and 
>> >> > some deep
>> >> > hacking, but that is the security issue with that.
>> >> 
>> >> Hmm that would mean there are three possibilities:
>> >> 1) Accept a Wildcard syntax like "bus:device.*", which would mean hide 
>> >> all functions of device.
>> 
>> > Which in this context actually makes sense. You probably don't want to use 
>> > the VF's in
>> > your host.
>> 
>> In my use cases i always hide all functions, and since my usb controllers 
>> have 7 functions, that leads to quite some long lines.
>> 
>> >> 2) Accept not providing the function as a wildcard "bus:device", would 
>> >> mean hide all functions of device.
>> 
>> > <nods>.
>> >> 
>> >> 3) Do nothing, the gained overview on grub lines isn't worth the effort 
>> >> :-)
>> 
>> > Heh!
>> 
>> > I think I like 2).
>> 
>> I think that would be the most simple and straightforward to implement, the 
>> only thing is that the .cfg files seem to use the "bus:device.*" scheme ...
>> Don't know if there are any other related cmd options for the kernel that 
>> use a certain syntax that could be preferred ?
>> 

> So Jan implemented this and it is in v3.7.


Yes i saw it :-)
Thx !


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