On Wed, 24 Aug 2016, Jan Kiszka wrote:
> On 2016-08-24 04:39, Thomas Gleixner wrote:
> > On Thu, 18 Aug 2016, Bjorn Helgaas wrote:
> >> I looked up the spec: PCI (not PCIe) r3.0, sec 3.2.2.3.4, says:
> >>
> >> A single-function device may optionally respond to all function
> >> numbers as the same function or may ... respond only to function 0
> >> and not respond to the other function numbers.
> >>
> >> I'm concerned that a single-function device that responds to all
> >> function numbers might break with this patch.
> >>
> >> [multi-function devices] are also required to always implement
> >> function 0 in the device.
> >>
> >> Here's the reason we can advance by 8 in the "Go find them" loop.
> >>
> >> If a single function device is detected (i.e., bit 7 in the Header
> >> Type register of function 0 is 0), no more functions for that Device
> >> Number will be checked. If a multi-function device is detected
> >> (i.e., bit 7 in the Header Type register of function 0 is 1), then
> >> all remaining Function Numbers will be checked.
> >>
> >> This patch does the opposite of what the first sentence recommends.
> >
> > Fair enough. We'll need to find a way to deal with that in jailhouse then.
>
> Wouldn't it also be an option to have this fine-grained scanning only
> activated if we detect to run over Jailhouse (which we have to anyway)?
> Such code hasn't been proposed for upstream yet, but we will eventually.
That might be an option.
Thanks,
tglx
