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

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Message-ID: <5614D110.5020308@cloudius-systems.com>
Date:	Wed, 7 Oct 2015 11:00:16 +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 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@...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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