Re: [Qemu-devel] [PATCH] hw/pci: disable pci-bridge's shpc by default

[Marcel Apfelbaum]

On 11/24/2016 06:06 AM, David Gibson wrote:
> On Wed, Nov 23, 2016 at 01:08:46PM +0200, Marcel Apfelbaum wrote:
> > On 11/22/2016 10:25 PM, Laurent Vivier wrote:
> > > On 22/11/2016 18:26, Marcel Apfelbaum wrote:
> > > > On 11/18/2016 05:52 PM, Andrew Jones wrote:
> > > > > On Wed, Nov 16, 2016 at 07:05:25PM +0200, Marcel Apfelbaum wrote:
> > > > > > On 11/16/2016 06:44 PM, Andrew Jones wrote:
> > > > > > > On Sat, Nov 05, 2016 at 06:46:34PM +0200, Marcel Apfelbaum wrote:
> > > > > > > > On 11/03/2016 09:40 PM, Michael S. Tsirkin wrote:
> > > > > > > > > On Thu, Nov 03, 2016 at 01:05:44PM +0200, Marcel Apfelbaum wrote:
> > > > > > > > > > On 11/03/2016 06:18 AM, Michael S. Tsirkin wrote:
> > > > > > > > > > > On Wed, Nov 02, 2016 at 05:16:42PM +0200, Marcel Apfelbaum wrote:
> > > > > > > > > > > > The shpc component is optional while  ACPI hotplug is used
> > > > > > > > > > > > for hot-plugging PCI devices into a PCI-PCI bridge.
> > > > > > > > > > > > Disabling the shpc by default will make slot 0 usable at boot time
> > > > > > > > > >
> > > > > > > > > > Hi Michael
> > > > > > > > > >
> > > > > > > > > > > at the cost of breaking all hotplug for all non-acpi users.
> > > > > > > > > >
> > > > > > > > > > Do we have a non-acpi user that is able to use the shpc component
> > > > > > > > > > as-is today?
> > > > > > > > >
> > > > > > > > > power and some arm systems I guess?
> > > > > > > >
> > > > > > > > Adding Andrew , maybe he can give us an answer.
> > > > > > >
> > > > > > > Not really :-) My lack of PCI knowledge makes that difficult. I'd be
> > > > > > > happy
> > > > > > > to help with an experiment though. Can you give me command line
> > > > > > > arguments,
> > > > > > > qmp commands, etc. that I should use to try it out? I imagine I should
> > > > > > > just boot an ARM guest using DT (instead of ACPI) and then attempt to
> > > > > > > hotplug a PCI device. I'm not sure, however, what, if any, special
> > > > > > > configuration I need in order to ensure I'm testing what you're
> > > > > > > interested in.
> > > > > >
> > > > > > Hi Drew,
> > > > > >
> > > > > >
> > > > > > Just run QEMU with '-device pci-bridge,chassis_nr=1,id=bridge1
> > > > > > -monitor stdio'
> > > > > > with an ARM guest using DT and wait until the guest finish booting.
> > > > > >
> > > > > > Then run at hmp:
> > > > > > device_add virtio-net-pci,bus=bridge1,id=net2
> > > > > >
> > > > > > Next run lspci in the guest to see the new device.
> > > > >
> > > > > Thanks for the instructions Marcel. Here's the results
> > > > >
> > > > >  $QEMU -machine virt,accel=$ACCEL -cpu $CPU -nographic -m 4096 -smp 8 \
> > > > >        -bios /usr/share/AAVMF/AAVMF_CODE.fd \
> > > > >        -device pci-bridge,chassis_nr=1,id=bridge1 \
> > > > >        -drive file=$FEDORA_IMG,if=none,id=dr0,format=qcow2 \
> > > > >        -device virtio-blk-pci,bus=bridge1,addr=01,drive=dr0,id=disk0 \
> > > > >        -netdev user,id=hostnet0 \
> > > > >        -device virtio-net-pci,bus=bridge1,addr=02,netdev=hostnet0,id=net0
> > > > >
> > > > >  # lspci
> > > > >  00:00.0 Host bridge: Red Hat, Inc. Device 0008
> > > > >  00:01.0 PCI bridge: Red Hat, Inc. QEMU PCI-PCI bridge
> > > > >  01:01.0 SCSI storage controller: Red Hat, Inc Virtio block device
> > > > >  01:02.0 Ethernet controller: Red Hat, Inc Virtio network device
> > > > >
> > > > >  (qemu) device_add virtio-net-pci,bus=bridge1,id=net2
> > > > >  Unsupported PCI slot 0 for standard hotplug controller. Valid slots are
> > > > >  between 1 and 31.
> > > > >
> > > > > (Tried again giving addr=03)
> > > > >
> > > > >  (qemu) device_add virtio-net-pci,bus=bridge1,id=net2,addr=03
> > > > >
> > > > > (Seemed to work, but...)
> > > > >
> > > > >  # lspci
> > > > >  00:00.0 Host bridge: Red Hat, Inc. Device 0008
> > > > >  00:01.0 PCI bridge: Red Hat, Inc. QEMU PCI-PCI bridge
> > > > >  01:01.0 SCSI storage controller: Red Hat, Inc Virtio block device
> > > > >  01:02.0 Ethernet controller: Red Hat, Inc Virtio network device
> > > > >
> > > > > (Doesn't show up in lscpi. So I guess it doesn't work)
> > > >
> > > > Hi Drew,
> > > > Thanks for confirming that it doesn't work.
> > > >
> > > > Michael asked if we can check the same for powerpc before
> > > > disabling the shpc by default.
> > > >
> > > > Adding David, Thomas and Laurrent, maybe they have time
> > > > to check it for powerpc.
> > >
> > > With this patch:
> > >
> > > # lspci
> > > 00:00.0 PCI bridge: Red Hat, Inc. QEMU PCI-PCI bridge
> > > 00:03.0 Unclassified device [00ff]: Red Hat, Inc Virtio memory balloon
> > > address@hidden ~]# QEMU 2.7.90 monitor - type 'help' for more information
> > > (qemu) device_add virtio-net-pci,bus=bridge1,id=net2
> > > Bus 'bridge1' does not support hotplugging
> > > (qemu) device_add virtio-net-pci,bus=bridge1,id=net2,addr=3
> > > Bus 'bridge1' does not support hotplugging
> > >
> > > Without this patch:
> > >
> > > # lspci
> > > 00:00.0 PCI bridge: Red Hat, Inc. QEMU PCI-PCI bridge
> > > 00:03.0 Unclassified device [00ff]: Red Hat, Inc Virtio memory balloon
> > > address@hidden ~]# QEMU 2.7.90 monitor - type 'help' for more information
> > > (qemu) device_add virtio-net-pci,bus=bridge1,id=net2
> > > Unsupported PCI slot 0 for standard hotplug controller. Valid slots are
> > > between 1 and 31.
> > > (qemu) device_add virtio-net-pci,bus=bridge1,id=net2,addr=3
> > > (qemu) [   37.342908] shpchp 0000:00:00.0: Latch close on Slot(3)
> > > [   37.342963] shpchp 0000:00:00.0: Button pressed on Slot(3)
> > > [   37.343003] shpchp 0000:00:00.0: Card present on Slot(3)
> > > [   37.344186] shpchp 0000:00:00.0: PCI slot #3 - powering on due to
> > > button press
> > > [   43.361827] shpchp 0000:00:00.0: No new device found
> >
> >
> > Hi Laurrent,
> > Thank you for the fast reply!
> >
> > What I see from the log is that ppc does use the shpc for hotplug,
> > but there is some implementation bug preventing it to work.
>
> That doesn't sound right.  ppc, or more correctly the pseries machine
> type, has it's own hotplug notification mechanism.  If we're trying to
> invoke shpc, I think something is wrong.

Hi David,

As you can see the shpc driver claims the pci-bridge slots and it responds
to the hot-plug events.

Anyway, what is the hotplug mechanism preferred by the pseries machine ?

Side note: what we want to understand is if using pci-bridges's shpc  by default
would help non x86 archs (since QEMU x86 machine uses ACPI based hot-plug).

Thanks,
Marcel

> > Drew, may I trouble one last time for the dmesg?
> > I think we would see exactly the same log.
> >
> >
> > Thanks,
> > Marcel
> >
> > > [   43.361867] shpchp 0000:00:00.0: Cannot add device at 0000:01:03
> > > [   43.363277] shpchp 0000:00:00.0: Latch open on Slot(3)
> > > [   43.363320] shpchp 0000:00:00.0: Button pressed on Slot(3)
> > > [   43.363360] shpchp 0000:00:00.0: Card not present on Slot(3)
> > > [   43.363506] shpchp 0000:00:00.0: PCI slot #3 - powering on due to
> > > button press
> > > [   48.371835] shpchp 0000:00:00.0: No adapter on slot(3)
> > >
> > > Laurent