[PATCH v2] docs: Document reserved PCI addresses for QEMU

[Michal Privoznik]

On 4/24/20 3:46 AM, Laine Stump wrote:
> On 4/21/20 2:00 PM, Michal Privoznik wrote:
>> >From time to time we are asked which PCI addresses are reserved
>> in QEMU. Let's document them in one place, it's easier than
>> reconstructing the list from the code each time.
>>
>> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>> ---
>>
>> diff to v1:
>> - All Laine's comment worked in, hopefully.
>>
>>   docs/pci-addresses.rst | 50 ++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 50 insertions(+)
>>
>> diff --git a/docs/pci-addresses.rst b/docs/pci-addresses.rst
>> index 885d50517a..4f123c7eb9 100644
>> --- a/docs/pci-addresses.rst
>> +++ b/docs/pci-addresses.rst
>> @@ -235,3 +235,53 @@ guest OS rather than as ``0001:08:00.1``, which 
>> is the address of the
>>   device on the host.
>>   Of course, all the rules and behaviors described above still apply.
>> +
>> +
>> +Reserved addresses
>> +==================
>> +
>> +Due to some historical reasons hypervisors might expect some PCI
>> +devices to appear at certain addresses instead of 'random' ones.
>> +For QEMU this is machine type and guest architecture dependant.
>> +But to give you at least a gist here is list of reserved PCI
>> +addresses:
>> +
>> +For ``I440FX`` the following devices are hard coded into QEMU and 
>> can't be
>> +moved or eliminated:
> 
> 
> Maybe instead of just saying "I440FX", you could say "the x86_64 
> architecture's 'i440fx'-based machinetypes" (or something like that), 
> both to let readers know that i440fx is a machinetype, as well as to 
> indicate that this isn't the exact name of the machinetype, but a class 
> of machinetypes.

Good point.

> 
> 
>> +
>> +============  ======================
>> +0000:00:00.0  Host bridge
>> +0000:00:01.0  ISA bridge
>> +0000:00:01.1  primary IDE controller
>> +0000:00:01.2  PIIX3 USB controller
>> +0000:00:01.3  ACPI (power management) and SMBus controller
>> +============  ======================
>> +
>> +The following addresses will be used as default ones for the 
>> corresponding
>> +devices (if the address is free or a different address wasn't 
>> provided for the
>> +device):
>> +
>> +============  ==================
>> +0000:00:02.0  primary video card
>> +============  ==================
> 
> 
> Do you think we need to explicitly say "it's okay to use this address 
> for any other device"? Or is what's said here enough. I'm undecided, 
> fine with it as is though.

I think "if the address is free" addresses that. But to be more explicit 
I'm adding what you suggested.

> 
> 
>> +
>> +
>> +For ``Q35`` the following devices are hard coded into QEMU and can't 
>> be moved
>> +or eliminated:
> 
> 
> Similar note for "q35" as for "i440fx"
> 
> 
>> +
>> +============  =======================
>> +0000:00:00.0  Host bridge
>> +0000:00:1f.2  primary SATA controller
>> +0000:00:1f.0  ISA bridge
>> +0000:00:1f.3  SMBus
>> +============  =======================
>> +
>> +The following addresses will be used as default ones for the 
>> corresponding
>> +devices (if the address is free or a different address wasn't 
>> provided for the
>> +device) because that's how real ``Q35`` would do it:
>> +
>> +============  ===============
>> +0000:00:1a.0  USB2 controller
>> +0000:00:1b.0  ICH9 sound chip
>> +0000:00:1d.0  USB2 controller
>> +============  ===============
> 
> 
> I notice you removed the dmi-to-pci-bridge. Which is fine with me, just 
> wanted you to know that I know that you know ;-)

Yes, that was intentional :-)

> 
> 
> Reviewed-by: Laine Stump <laine at redhat.com>
> 
> 

Pushed, thanks!

Michal