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

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Date:	Wed, 7 Oct 2015 11:01:03 +0300
From:	Vlad Zolotarov <vladz@...udius-systems.com>
To:	Avi Kivity <avi@...lladb.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Alex Williamson <alex.williamson@...hat.com>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>, hjk@...sjkoch.de,
	Jonathan Corbet <corbet@....net>,
	"Bruce.Richardson@...el.com" <bruce.richardson@...el.com>,
	avi@...udius-systems.com, gleb@...udius-systems.com,
	Alexander Duyck <alexander.duyck@...il.com>
Subject: Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support



On 10/07/15 11:00, Vlad Zolotarov wrote:
>
>
> 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 

By default I meant.

> 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@...hat.com <mailto:alex.williamson@...hat.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@...hat.com
>>>     <mailto:alex.williamson@...hat.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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