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SubjectRe: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support
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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@redhat.com <mailto:alex.williamson@redhat.com>> 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@redhat.com
>> <mailto:alex.williamson@redhat.com>> 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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