Re: [Xen-users] Marvell, IOMMU/VT-d, and pci-phantom

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.06.13 at 16:10, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Fri, 2013-06-28 at 14:59 +0100, Jan Beulich wrote:
>>  So
>> 
>> pci-phantom=06:00,1
>> 
>> should do, provided this is a single-function device.
> 
> So what does stride actually mean? To me it suggests every N-th device,
> but in that case how do we know how many there are in total?

Every N-th function. With there being up to 8 functions per device,
stride one means all of them, stride 2 every even one, and stride 4
functions 0 and 4.

On a single function device it is generally safe to use stride 1. On
multi function devices stride must not result in collisions with one
of the other functions.

>> > Jan, since you wrote this patch for Marvell devices I suppose you know
>> > the right incantation for this bit of hardware?
>> 
>> The specific hardware doesn't matter, we're basically just overriding
>> rwo bits that a device behaving this way should have set in its PCIe
>> capability structure (i.e. the resulting behavior is generic).
> 
> I'm not 100% convinced that requiring users to understand the PCIe
> capability structures here is "fair", but I suppose it is an advanced
> feature.

Oh, that part of the response was more to you than the original
user.

> Assuming you meant "two" not "rwo", which two bits are they?

PCI_EXP_DEVCAP_PHANTOM in terms of xen/include/xen/pci_regs.h.

Jan


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