Re: [Xen-devel] Question about the XEN platform pci

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Apr 12, 2016 at 05:33:47PM +0200, karim.allah.ahmed@xxxxxxxxx wrote:
> The INTx interrupt of this platform device can be used by Xen in HVM case to
> notify the guest of pending events in the event channel. However that's 
> usually
> not used in favor of vector callbacks support in Xen where a vector is 
> injected
> directly to the vCPU bypassing LAPIC.
> 
> (that said, the platform-pci driver in linux is actually broken when vector
> callbacks are not used anyway)

Oh? Is there an report/bug somewhere?

Thanks!
> 
> I also think that the grant-table lives on this PCI device MMIO BAR (?!)

The area may be usurped for grant-table as the OS won't touch that memory
area (it after all belongs to the device).
> 
> If you looked at hw/i386/xen/xen_platform.c in QEMU source , you will get a
> general idea what this device is supposed todo (like logging to syslog stuff
> for example).
> 
> That said the platform device is really not fully utilized anyway in Linux.
> 
> On Tue, Apr 12, 2016 at 4:09 PM, Konrad Rzeszutek Wilk
> <konrad.wilk@xxxxxxxxxx> wrote:
> > On Tue, Apr 12, 2016 at 02:19:48AM +0000, Wu, Bob wrote:
> >>
> >> Really thanks for your reply.
> >
> > Hey!
> >
> > CC-ing Xen-devel back on. Please do not drop it and please don't
> > top-post.
> >>
> >> Can you explain a little more?
> >
> > I am not sure what you want me to explain. Perhaps if you
> > read http://xenbits.xen.org/docs/unstable/misc/hvm-emulated-unplug.html
> > it may become clearer?
> >
> >> Is the xen platform pci driver the only purpose for telling QEMU  that 
> >> don’t emulate the IDE driver?
> >
> > And network.
> >> I think it can be done by a simple way, but don't need use this huge 
> >> platform driver.
> >
> > ?
> >>
> >> I guess this is for PCI pass through in XEN HVM mode, but don't sure.
> >
> > No.
> >>
> >> Thanks,
> >> Bob
> >>
> >>
> >> -----Original Message-----
> >> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> >> Sent: 2016年4月11日 22:24
> >> To: Wu, Bob
> >> Cc: xen-devel@xxxxxxxxxxxxx
> >> Subject: Re: [Xen-devel] Question about the XEN platform pci
> >>
> >> On Fri, Apr 08, 2016 at 08:52:08AM +0000, Wu, Bob wrote:
> >> >
> >> > Sorry bother, I read the XEN source code recently, and found the XEN
> >> > platform PCI code under drivers/xen/platform-pci.c, and I can't fully 
> >> > under this driver's affect, can anybody explain a little for me?
> >> >
> >> > Is the platform PCI driver for PV-split-PCI-driver-model such as the 
> >> > pci-frontend/pci-backend? or for PCI pass-through model? Or for other 
> >> > purpose?
> >> > I saw the xenbus_pcifront_driver/ xenbus_xen_pcibk_driver are registered 
> >> > on XENBUS, so I guess the platform-PCI-driver is not for PV PCI driver.
> >> >
> >>
> >> It is for the QEMU driver. To tell QEMU to stop emulating the IDE/network.
> >>
> >> > Really thank you for your replay.
> >> >
> >> > Thanks,
> >> > Bob
> >> >
> >>
> >> > _______________________________________________
> >> > Xen-devel mailing list
> >> > Xen-devel@xxxxxxxxxxxxx
> >> > http://lists.xen.org/xen-devel
> >>
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel
> 
> 
> 
> -- 
> Karim Allah Ahmed.

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