On Wed, 2014-08-20 at 06:04 +0000, Gonglei (Arei) wrote: > > On Wed, 2014-08-20 at 06:39 +0200, Knut Omang wrote: > > > On Wed, 2014-08-20 at 02:16 +0000, Gonglei (Arei) wrote: > > > > > -----Original Message----- > > > > > From: Michael S. Tsirkin [mailto:m...@redhat.com] > > > > > Sent: Wednesday, August 20, 2014 5:19 AM > > > > > To: Gonglei (Arei) > > > > > Cc: Paolo Bonzini; Marcel Apfelbaum; qemu-devel@nongnu.org; > > > > > imamm...@redhat.com; arm...@redhat.com; Huangweidong (C) > > > > > Subject: Re: [Question] Why doesn't PCIe hotplug work for Q35 machine? > > > > > > > > > > On Tue, Aug 19, 2014 at 06:25:56AM +0000, Gonglei (Arei) wrote: > > > > > > > >> Subject: Re: [Question] Why doesn't PCIe hotplug work for Q35 > > machine? > > > > > > > >> > > > > > > > >> On Sun, 2014-08-17 at 13:00 +0200, Michael S. Tsirkin wrote: > > > > > > > >>> On Fri, Aug 15, 2014 at 07:33:29AM +0000, Gonglei (Arei) > > > > > > > >>> wrote: > > > > > > > >>>> Hi, > > > > > > > >>>> > > > > > > > >>>> I noticed that the qemu-2.1 release change log says > > > > > > > >>>> " PCIe: Basic hot-plug/hot-unplug support for Q35 machine." > > > > > > > >>>> And then I made a testing for the hotplugging function of > > > > > > > >>>> Q35. > > > > > > > >>>> But I'm failed, and I got the dmesg log in guest os as below: > > > > > > > >>>> > > > > > > > >>>> [ 159.035250] Pciehp 0000:05:00.0:pcie24: Button pressed on > > Slot (0 - > > > > > 4) > > > > > > > >>>> [ 159.035274] Pciehp 0000:05:00.0:pcie24: Card present on > > > > > > > >>>> Slot > > (0 - 4) > > > > > > > >>>> [ 159.036517] Pciehp 0000:05:00.0:pcie24: PCI slot #0 - 4 - > > powering > > > > > on > > > > > > > due > > > > > > > >> to button press. > > > > > > > >>>> [ 159.188049] Pciehp 0000:05:00.0:pcie24: Failed to check > > > > > > > >>>> link > > status > > > > > > > >>>> [ 159.201968] Pciehp 0000:05:00.0:pcie24: Card not present on > > Slot (0 > > > > > - 4) > > > > > > > >>>> [ 159.202529] Pciehp 0000:05:00.0:pcie24: Already disabled on > > Slot (0 > > > > > - 4) > > > > > > > >>>> > > > > > > > >>>> Steps of testing: > > > > > > > >>>> > > > > > > > >>>> #1. QEMU version: > > > > > > > >>>> > > > > > > > >>>> The lateset master tree source. > > > > > > > >>>> > > > > > > > >>>> #2. Command line: > > > > > > > >>>> > > > > > > > >>>> ./qemu-system-x86_64 -enable-kvm -m 2048 -machine q35 > > -device > > > > > > > >> ide-drive,bus=ide.2,drive=MacHDD \ > > > > > > > >>>> -drive > > > > > > > id=MacHDD,if=none,file=/mnt/sdb/gonglei/image/redhat_q35.img > > > > > > > >> -monitor stdio -vnc :10 -readconfig ../docs/q35-chipset.cfg > > > > > > > >>>> QEMU 2.0.93 monitor - type 'help' for more information > > > > > > > >>>> (qemu) device_add > > > > > > > >> > > virtio-net-pci,id=nic2,bus=pcie-switch-downstream-port-1-1,addr=1.0 > > > > > > > >>> > > > > > > > >>> I don't think you can use any slot except slot 0 for pci > > > > > > > >>> express. > > > > > > > > > > > > > > > > OK. Does the PCIe specification say that? > > > > > > > > I appreciate very much that you explain more. > > > > > > > > > > > > > > The closest I could find is in "7.3. Configuration Transaction > > > > > > > Rules"/"7.3.1. Device Number": > > > > > > > > > > > > > > With non-ARI Devices, PCI Express components are restricted to > > > > > > > implementing a single Device Number on their primary interface > > (Upstream > > > > > > > Port) [...] Downstream Ports that do not have ARI Forwarding > > > > > > > enabled > > > > > > > must associate only Device 0 with the device attached to the > > > > > > > Logical > > Bus > > > > > > > representing the Link from the Port. Configuration Requests > > > > > > > targeting the Bus Number associated with a Link specifying Device > > Number > > > > > > > 0 are delivered to the device attached to the Link; Configuration > > > > > > > Requests specifying all other Device Numbers (1-31) > > > > > > > must be terminated by the Switch Downstream Port or the Root Port > > with > > > > > > > an Unsupported Request Completion Status (equivalent to Master > > Abort in > > > > > > > PCI). > > > > > > > > > > > > > Thanks a lot, Paolo. > > > > > > And I found another issue when cold-plugging don't using slot 0, the > > PCIe > > > > > device also can't > > > > > > be searched in guest os. > > > > > > > > > > > > So, I have some questions and ideas: > > > > > > > > > > > > 1. Does qemu support ARI Forwarding for PCIe at present? If yes, how > > to > > > > > enable it ? > > > > > > > > > > What do you mean by forwarding? > > > > > > > > Just ARI supporting, came from the PCIe spec. > > > > > > > > > What would you like to do? > > > > > > > > I just want to add some check. Because it made me confused, > > > > and other people IMHO. > > > > > > > > > We do have code to emulate ARI, I don't think many people > > > > > tested it so it's likely incomplete. > > > > > > > > > Yes, you have said (pcie_ari_init). > > > > > > I have actually been playing around with this a bit in the context of > > > SR/IOV, and have some patches waiting to be posted. I haven't had any > > > success with the downstream switch - as you indicate, pieces may be > > > missing, but in my case, using the ioh3420 root port worked fine after > > > setting the ARI forwarding capability and a few other minor fixes that > > > may even be considered trivial patches. I will put my acts together and > > > rebase these and post in a separate mail. > > > > > > Basically I am able to run and hotplug an ARI capable device on any root > > > port. So instead of using the downstream switch, you could just add > > > another ioh3420 for your next device, if that suits your needs. > > > > > > Note that there are two places to add "ARI support", one is the > > > forwarding capability of bridges/switches, the other is the device's > > > capability to be an ARI device, represented by the ARI PCIe capability. > > > > Hi, you are welcome to post your patches. > At present, both root roots and downstream ports > are not support a device with slot > 0.
Working on it right now ;-) > > > > > > 2. If not, we should add some check for PCIe root ports and > > > > > > downstream > > > > > ports, > > > > > > meanwhile add explaining document. > > > > > > > > > > You want an attempt to add a device at slot !=0 to report an error? > > > > > We can do this if device at slot 0 does not have ARI support. > > > > > Seems like a low priority issue I think. > > > > > > If I understand the spec right it is devices in slots > 0 that is > > > > Sorry - just noticed that a confusing "not" was lost here - I meant: > > > > "it is not devices in slots > 0 that are" > > > > > limited, it is that each slot may only expose one device, even if that > > > device has more than 8 functions and supports ARI, in which case we > > > should create a master abort. > > PCIe spec says that Downstream Ports that do not have ARI Forwarding > enabled must associate only Device 0 with the device attached to the Logical > Bus representing the Link from the Port. Yes, so the way I understand it is that lets say you have a device with 16 logical functions, then only functions 0-7 represented with device ID 0.0-0.7 may be exposed for that port, as function #9 and above would get device ID 1.0-1.7 which would require ARI forwarding. Knut > > > But the better solution in my view would > > > be just to implement ARI forwarding.. > > > Yes. > > Best regards, > -Gonglei
