Re: [PATCH v3 0/3] uio: add MSI/MSI-X support to uio_pci_generic driver

[Avi Kivity]

On 10/07/2015 01:25 PM, Michael S. Tsirkin wrote:
> On Tue, Oct 06, 2015 at 07:09:11PM +0300, Avi Kivity wrote:
> > On 10/06/2015 06:15 PM, Michael S. Tsirkin wrote:
> > > > While it is possible that userspace malfunctions and accidentally programs
> > > > MSI incorrectly, the risk is dwarfed by the ability of userspace to program
> > > > DMA incorrectly.
> > > That seems to imply that for the upstream kernel this is not a valid usecase at all.
> > That is trivially incorrect, upstream pci_uio_generic is used with dpdk for
> > years.
> dpdk used to do polling for years. patch to use interrupts was posted in
> june 2015.

dpdk used interrupts long before that.

> >   Are dpdk applications an invalid use case?
> The way dpdk is using UIO/sysfs is borderline at best, and can't be used
> to justify new interfaces.  They have a more secure mode using VFIO.
> That one's more reasonable.

Maybe this was not stressed enough times, but not all configurations 
have an iommu, or want to use one.

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