Re: [Qemu-riscv] [Qemu-devel] [qemu-s390x] [RFC PATCH 1/3] hw/Kconfig: PCI bus implies PCI_DEVICES

[Markus Armbruster <armbru@redhat.com>]

Thomas Huth <thuth@redhat.com> writes:

> On 16/07/2019 15.06, Markus Armbruster wrote:
[...]
>> 2. We want a way to Kconfig the PCI devices that work, i.e. only the
>>    ones that support MSI or MSI-X.
>> 
>> I don't like calling devices without any MSI capability "classic" or
>> "conventional devices".  I'd rather call them "MSI-capable" or
>> "MSI/MSI-X devices".
>
> But you still need a config switch that you can set to enable the
> non-MSI devices ... what's so wrong with "conventional" if that's even
> the wording from the PCI SIG?

PCI Express Base Specification, rev. 3.0, section Terms and
Acronyms:

    conventional PCI    Behavior or features that conform to the PCI
                        Local Bus Specification.

In other words, "conventional PCI" is non-Express PCI.

A PCI Express device *must* support MSI or MSI-X.  See PCI Express Base
Specification, rev. 3.0, section 7.7. MSI and MSI-X Capability
Structures.

A "conventional" PCI device *may* support MSI or MSI-X.  See PCI Local
Bus Specification Revision 3.0 section 6.8.  Message Signaled
Interrupts.

Conflating MSI-capable with conventional vs. Express is therefore wrong.

[...]