linux-kernel - Re: [PATCHv4] uio: add generic driver for PCI 2.3 devices

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Date:	Mon, 20 Jul 2009 21:19:19 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	"Hans J. Koch" <hjk@...utronix.de>, anthony@...emonkey.ws,
	avi@...hat.com, kvm@...r.kernel.org, chrisw@...hat.com,
	gregkh@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4] uio: add generic driver for PCI 2.3 devices

On Mon, Jul 20, 2009 at 10:17:02AM -0700, Jesse Barnes wrote:
> On Wed, 15 Jul 2009 23:39:11 +0200
> "Hans J. Koch" <hjk@...utronix.de> wrote:
> 
> > On Wed, Jul 15, 2009 at 11:13:40PM +0300, Michael S. Tsirkin wrote:
> > > This adds a generic uio driver that can bind to any PCI device.
> > > First user will be virtualization where a qemu userspace process
> > > needs to give guest OS access to the device.
> > > 
> > > Interrupts are handled using the Interrupt Disable bit in the PCI
> > > command register and Interrupt Status bit in the PCI status
> > > register.  All devices compliant to PCI 2.3 (circa 2002) and all
> > > compliant PCI Express devices should support these bits.  Driver
> > > detects this support, and won't bind to devices which do not
> > > support the Interrupt Disable Bit in the command register.
> > > 
> > > It's expected that more features of interest to virtualization will
> > > be added to this driver in the future. Possibilities are: mmap for
> > > device resources, MSI/MSI-X, eventfd (to interface with kvm), iommu.
> > 
> > Well, I'm not enough of a PCI expert to tell whether your 2.3-test
> > works or not (can it have side effects, e.g. trigger an interrupt
> > when you toggle that bit?). I've added Jesse Barnes to Cc: since you
> > modify a PCI core header file. If there are no objections from the
> > PCI people, I guess we can take this.
> 
> pci_reg.h portion looks fine to me, and only supporting devices with
> the interrupt disable bit certainly simplifies things.  There were some
> other questions on the thread though (like Greg's similar driver); not
> sure if you've answered those yet.

Yes, and Greg seems satisfied :). See 20090716181919.GB27811@...e.de.
Chris Wright (author of pci-stub that was mentioned) also acked the
patch.

> -- 
> Jesse Barnes, Intel Open Source Technology Center
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