Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support

[Vlad Zolotarov]

On 10/07/15 09:53, Avi Kivity wrote:
> On 10/07/2015 12:58 AM, Stephen Hemminger wrote:
> > Go ahead and submit a seperate taint bit for UIO as a patch.
>
> Taint should only be applied if bus mastering is enabled (to avoid 
> annoying the users of the original uio use case)

Pls., note that this series would enable the legacy INT#X mode if 
possible and this, of course, without enabling bus mastering and without 
tainting the kernel.
This means that the current users of uio_pci_generic won't feel/get any 
difference after/if these patches are applied since before these patches 
it could only be used with the devices that do have INT#X capability.

> > On Tue, Oct 6, 2015 at 10:41 PM, Alex Williamson 
> > <alex.williamson@xxxxxxxxxx <mailto:alex.williamson@xxxxxxxxxx>> wrote:
> >
> >     On Tue, 2015-10-06 at 22:32 +0100, Stephen Hemminger wrote:
> >     > On Tue, 06 Oct 2015 12:51:20 -0600
> >     > Alex Williamson <alex.williamson@xxxxxxxxxx
> >     <mailto:alex.williamson@xxxxxxxxxx>> wrote:
> >     >
> >     > > Of course this is entirely unsafe and this no-iommu driver
> >     should taint
> >     > > the kernel, but it at least standardizes on one userspace API
> >     and you're
> >     > > already doing completely unsafe things with uio.  vfio should be
> >     > > enlightened at least to the point that it allows only
> >     privileged users
> >     > > access to devices under such a (lack of) iommu
> >     >
> >     > I agree with the design, but not with the taint argument.
> >     > (Unless you want to taint any and all use of UIO drivers which can
> >     >  already do this).
> >
> >     Yes, actually, if the bus master bit gets enabled all bets are
> >     off.  I
> >     don't see how that leaves a supportable kernel, so we might as well
> >     taint it.  Isn't this exactly why we taint for proprietary
> >     drivers, we
> >     have no idea what it has mucked with in kernel space. This just moves
> >     the proprietary driver out to userspace without an iommu to
> >     protect the
> >     host.  Thanks,
> >
> >     Alex

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