[SeaBIOS] [Qemu-devel] [PATCH v3 5/5] docs: update documentation considering PCIE-PCI bridge

[Marcel Apfelbaum]

On 02/08/2017 17:16, Laszlo Ersek wrote:
> On 08/02/17 15:47, Michael S. Tsirkin wrote:
>> On Wed, Aug 02, 2017 at 12:23:46AM +0200, Laszlo Ersek wrote:
>>> On 08/01/17 23:39, Michael S. Tsirkin wrote:
>>>> On Wed, Aug 02, 2017 at 12:33:12AM +0300, Alexander Bezzubikov wrote:
>>>>> 2017-08-01 23:31 GMT+03:00 Laszlo Ersek <lersek at redhat.com>:
>>>>>> (Whenever my comments conflict with Michael's or Marcel's, I defer to them.)
>>>>>>
>>>>>> On 07/29/17 01:37, Aleksandr Bezzubikov wrote:
>>>>>>> Signed-off-by: Aleksandr Bezzubikov <zuban32s at gmail.com>
>>>>>>> ---
>>>>>>>   docs/pcie.txt            |  46 ++++++++++--------
>>>>>>>   docs/pcie_pci_bridge.txt | 121 +++++++++++++++++++++++++++++++++++++++++++++++
>>>>>>>   2 files changed, 147 insertions(+), 20 deletions(-)
>>>>>>>   create mode 100644 docs/pcie_pci_bridge.txt
>>>>>>>
>>>>>>> diff --git a/docs/pcie.txt b/docs/pcie.txt
>>>>>>> index 5bada24..338b50e 100644
>>>>>>> --- a/docs/pcie.txt
>>>>>>> +++ b/docs/pcie.txt
>>>>>>> @@ -46,7 +46,7 @@ Place only the following kinds of devices directly on the Root Complex:
>>>>>>>       (2) PCI Express Root Ports (ioh3420), for starting exclusively PCI Express
>>>>>>>           hierarchies.
>>>>>>>
>>>>>>> -    (3) DMI-PCI Bridges (i82801b11-bridge), for starting legacy PCI
>>>>>>> +    (3) PCIE-PCI Bridge (pcie-pci-bridge), for starting legacy PCI
>>>>>>>           hierarchies.
>>>>>>>
>>>>>>>       (4) Extra Root Complexes (pxb-pcie), if multiple PCI Express Root Buses
>>>>>>
>>>>>> When reviewing previous patches modifying / adding this file, I
>>>>>> requested that we spell out "PCI Express" every single time. I'd like to
>>>>>> see the same in this patch, if possible.
>>>>>
>>>>> OK, I didn't know it.
>>>>>
>>>>>>
>>>>>>> @@ -55,18 +55,18 @@ Place only the following kinds of devices directly on the Root Complex:
>>>>>>>      pcie.0 bus
>>>>>>>      ----------------------------------------------------------------------------
>>>>>>>           |                |                    |                  |
>>>>>>> -   -----------   ------------------   ------------------   --------------
>>>>>>> -   | PCI Dev |   | PCIe Root Port |   | DMI-PCI Bridge |   |  pxb-pcie  |
>>>>>>> -   -----------   ------------------   ------------------   --------------
>>>>>>> +   -----------   ------------------   -------------------   --------------
>>>>>>> +   | PCI Dev |   | PCIe Root Port |   | PCIE-PCI Bridge |   |  pxb-pcie  |
>>>>>>> +   -----------   ------------------   -------------------   --------------
>>>>>>>
>>>>>>>   2.1.1 To plug a device into pcie.0 as a Root Complex Integrated Endpoint use:
>>>>>>>             -device <dev>[,bus=pcie.0]
>>>>>>>   2.1.2 To expose a new PCI Express Root Bus use:
>>>>>>>             -device pxb-pcie,id=pcie.1,bus_nr=x[,numa_node=y][,addr=z]
>>>>>>> -      Only PCI Express Root Ports and DMI-PCI bridges can be connected
>>>>>>> +      Only PCI Express Root Ports, PCIE-PCI bridges and DMI-PCI bridges can be connected
>>>>>>
>>>>>> It would be nice if we could keep the flowing text wrapped to 80 chars.
>>>>>>
>>>>>> Also, here you add the "PCI Express-PCI" bridge to the list of allowed
>>>>>> controllers (and you keep DMI-PCI as permitted), but above DMI was
>>>>>> replaced. I think these should be made consistent -- we should make up
>>>>>> our minds if we continue to recommend the DMI-PCI bridge or not. If not,
>>>>>> then we should eradicate all traces of it. If we want to keep it at
>>>>>> least for compatibility, then it should remain as fully documented as it
>>>>>> is now.
>>>>>
>>>>> Now I'm beginning to think that we shouldn't keep the DMI-PCI bridge
>>>>> even for compatibility and may want to use a new PCIE-PCI bridge
>>>>> everywhere (of course, except some cases when users are
>>>>> sure they need exactly DMI-PCI bridge for some reason)
>>>>
>>>> Can dmi-pci support shpc? why doesn't it? For compatibility?
>>>
>>> I don't know why, but the fact that it doesn't is the reason libvirt
>>> settled on auto-creating a dmi-pci bridge and a pci-pci bridge under
>>> that for Q35. The reasoning was (IIRC Laine's words correctly) that the
>>> dmi-pci bridge cannot receive hotplugged devices, while the pci-pci
>>> bridge cannot be connected to the root complex. So both were needed.
>>>
>>> Thanks
>>> Laszlo
>>
>> OK. Is it true that dmi-pci + pci-pci under it will allow hotplug
>> on Q35 if we just flip the bit in _OSC?
> 
> Marcel, what say you?... :)
> 

Will test and get back to you (it may actually work)

Thanks,
Marcel