Re: [PATCH 0/6] MSI portability cleanups

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

> You can read config space, but it's not clear to me if the HV is allowed
> to filter it and hide things. 

I've seen it do it for example with EADS bridges. I haven't seen doing
it with devices (other than hiding entire functions) but I wouldn't
exclude it...

> It's also possible that the device
> supports MSI, but for some reason the HV doesn't allow it on that device
> etc. so you really have to ask the HV if it's enabled. So pci_find_cap()
> shouldn't crash or anything, but it may lie to you.

Yup.

> One thing I did like about my code, is that pci_enable_msi() and
> pci_enable_msix() are just small wrappers around generic_enable_msi() -
> which does all the work, and is the same regardless of whether it's an
> MSI or MSI-X. Although that's facilitated by the type arg which you
> don't like.

Part of the reason is you make MSI look like MSI-X (a vector of 1 entry)
while Eric does the opposite.

Ben.