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

["karim.allah.ahmed@xxxxxxxxx" <karim.allah.ahmed@xxxxxxxxx>]

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)

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

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
>>
>
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-- 
Karim Allah Ahmed.

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