Re: [Qemu-devel] [PATCH RFC] docs: add PCIe devices placement guidelines

[Laszlo Ersek]

On 09/01/16 15:51, Marcel Apfelbaum wrote:
> On 09/01/2016 04:27 PM, Peter Maydell wrote:
>> On 1 September 2016 at 14:22, Marcel Apfelbaum <address@hidden> wrote:
>>> Proposes best practices on how to use PCIe/PCI device
>>> in PCIe based machines and explain the reasoning behind them.
>>>
>>> Signed-off-by: Marcel Apfelbaum <address@hidden>
>>> ---
>>>
>>> Hi,
>>>
>>> Please add your comments on what to add/remove/edit to make this doc
>>> usable.
>>
> 
> Hi Peter,
> 
>> As somebody who doesn't really understand the problem space, my
>> thoughts:
>>
>> (1) is this intended as advice for developers writing machine
>> models and adding pci controllers to them, or is it intended as
>> advice for users (and libvirt-style management layers) about
>> how to configure QEMU?
>>
> 
> Is it intended for management layers as they have no way to
> understand how to "consume" the Q35 machine,
> but also for firmware developers (OVMF/SeaBIOS) to help them
> understand the usage model so they can optimize IO/MEM
> resources allocation for both boot time and hot-plug.
> 
> QEMU users/developers can also benefit from it as the PCIe arch
> is more complex supporting both PCI/PCIe devices and
> several PCI/PCIe controllers with no clear rules on what goes where.
> 
>> (2) it seems to be a bit short on concrete advice (either
>> "you should do this" instructions to machine model developers,
>> or "use command lines like this" instructions to end-users.
>>
> 
> Thanks for the point. I'll be sure to add detailed command line examples
> to the next version.

I think that would be a huge benefit!

(I'll try to read the document later, and come back with remarks.)

Thanks!
Laszlo