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

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

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.
2) Accept not providing the function as a wildcard "bus:device", would mean 
hide all functions of device.

3) Do nothing, the gained overview on grub lines isn't worth the effort :-)

>> 
>> --
>> Regards,
>> 
>> Sander
>> 




-- 
Best regards,
 Sander                            mailto:linux@xxxxxxxxxxxxxx


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