Re: [Xen-devel] xl pci-attach silently fails the first time

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

On Mon, Dec 01, 2014 at 02:32:44PM +0100, Olaf Hering wrote:
> On Mon, Dec 01, Olaf Hering wrote:
> 
> > # xl pci-assignable-add 01:10.0
> > # xl pci-assignable-list
> > 0000:01:10.0
> > # xl create -f domU.cfg
> > # xl console domU
> > ## lspci gives just emulated PCI devices
> 
> ttyS0:Rescue:~ # lspci 
> 00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
> 00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
> 00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
> 00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
> 00:02.0 Unassigned class [ff80]: XenSource, Inc. Xen Platform Device (rev 01)
> 00:03.0 VGA compatible controller: Cirrus Logic GD 5446
> 00:04.0 Ethernet controller: Realtek Semiconductor Co., Ltd. 
> RTL-8100/8101L/8139 PCI Fast Ethernet Adapter (rev ff)
> 
> > ## detach from domU console
> > # xl pci-attach domU 0000:01:10.0
> > # xl pci-list domU
> > Vdev Device
> > 04.0 0000:01:10.0
> > 
> > # xl console domU
> > ## lspci gives just emulated PCI devices
> 
> ttyS0:Rescue:~ # lspci 
> 00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
> 00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
> 00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
> 00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
> 00:02.0 Unassigned class [ff80]: XenSource, Inc. Xen Platform Device (rev 01)
> 00:03.0 VGA compatible controller: Cirrus Logic GD 5446
> 00:04.0 Ethernet controller: Realtek Semiconductor Co., Ltd. 
> RTL-8100/8101L/8139 PCI Fast Ethernet Adapter (rev 01)
> 
> > ## detach from domU console
> > # xl pci-detach domU 0000:01:10.0
> Now lspci shows that the emulated network card is gone.

> ttyS0:Rescue:~ # lspci 
> 00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
> 00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
> 00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
> 00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
> 00:02.0 Unassigned class [ff80]: XenSource, Inc. Xen Platform Device (rev 01)
> 00:03.0 VGA compatible controller: Cirrus Logic GD 5446
> 
> > # xl pci-attach domU 0000:01:10.0
> > # xl pci-list domU
> > Vdev Device
> > 04.0 0000:01:10.0
> > # xl console domU
> > ## lspci shows now also the assigned host device
> 
> 
> So the actual bug is that the very first time after pci-attach the guests
> "00:04.0" PCI device is (most likely) replaced with the host PCI device. Just
> the guest does not notice that "00:04.0" was actually already gone after 
> unplug.

That is odd - I see any device 'hot-plugged' being added at 00:05 and further.

> 
> I wonder why the unplug code in xen_platform.c does just a qdev_free() instead
> of a real pci-detach kind of thing. I'm sure this could be done at least for
> emulated network cards.
> 
> Olaf
> 
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