linux-kernel - Re: [PATCH v3 0/3] uio: add MSI/MSI-X support to uio_pci

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Date:	Wed, 7 Oct 2015 13:25:10 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Avi Kivity <avi@...lladb.com>
Cc:	Avi Kivity <avi@...udius-systems.com>,
	Vlad Zolotarov <vladz@...udius-systems.com>,
	linux-kernel@...r.kernel.org, hjk@...sjkoch.de, corbet@....net,
	gregkh@...uxfoundation.org, bruce.richardson@...el.com,
	gleb@...udius-systems.com, stephen@...workplumber.org,
	alexander.duyck@...il.com
Subject: Re: [PATCH v3 0/3] uio: add MSI/MSI-X support to uio_pci_generic
 driver

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.

>  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.

-- 
MST
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