Re: [PATCH 0/1] uio_pci_generic: extensions to allow access for non-privileged processes

Avi Kivity
2010-04-02T06:43:49Z

On 04/01/2010 10:24 PM, Tom Lyon wrote:
>
>> But there are multiple msi-x interrupts, how do you know which one
>> triggered?
>>
> You don't. This would suck for KVM, I guess, but we'd need major rework of the
> generic UIO stuff to have a separate event channel for each MSI-X.
>

Doesn't it suck for non-kvm in the same way? Multiple vectors are there
for a reason. For example, if you have a multiqueue NIC, you'd have to
process all queues instead of just the one that triggered.

> For my purposes, collapsing all the MSI-Xs into one MSI-look-alike is fine,
> because I'd be using MSI anyways if I could. The weird Intel 82599 VF only
> supports MSI-X.
>
> So one big question is - do we expand the whole UIO framework for KVM
> requirements, or do we split off either KVM or non-VM into a separate driver?
> Hans or Greg - care to opine?
>

Currently kvm does device assignment with its own code, I'd like to
unify it with uio, not split it off.

Separate notifications for msi-x interrupts are just as useful for uio
as they are for kvm.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.