Chipset support for Message Signaled Interrupts (MSI)

[RicV]

Hi,

I am working on a custom PCI device model, plugged into VirtualBox via PDM. It's mostly working, lspci for example shows it's present. But I am having a problem with Message Signaled Interrupts (MSI).

The following quote from Ch.3 of the VirtualBox User Manual implies that the ICP9 chipset must be used for MSI support, and I have seen supporting evidence in web searches and VBox source code (OSE 5.0.16 tarball).

...VirtualBox 4.0 introduced an emulation of the more modern ICH9 chipset, which supports PCI express,
three PCI buses, PCI-to-PCI bridges and Message Signaled Interrupts (MSI)...

Can someone confirm or refute with certainty that the PIIX3 chipset does not support MSI and ICH9 is required for device models using MSI?

How worried should I be about this excerpt from the same paragraph? A quick test of ICH9 VM did not go well. I've actually tried with Fedora 23, Fedora 18 and Ubuntu 14 guests (all 64-bit) without success, but not yet dug into it because this quote worries me.

Note that the ICH9 support is experimental and not recommended for guest operating systems which do not require it.

[Perryg]

I use ICH9 all the time.

[RicV]

Thanks, Perry. I will report on the troubles I am facing with ICH9 in a separate thread once I have more information. Meanwhile, do you know the answer to whether MSI is supported with the PIIX3 chipset is selected? I am at a crossroads where I must either figure out why MSI is not working with PIIX3 (if that's even possible), or continue to get an ICH9 VM working well.

[Perryg]

Sorry not I can't. I assumed it would but for a definitive answer you would need to ask the DEVs. Try their IRC channel or mailing list. https://www.virtualbox.org/wiki/Community

[RicV]

To close the loop on this...

I heard back from the developers that yes, if you want MSI support, then you must use the ICH9 chipset. And I was able to set up VMs with Fedora 23, Fedora 18, Ubuntu 14 and Win8.1 guests (all 64-bit). The troubles I mentioned above were self inflicted, by changing the chipset in an existing VM. Any VM in which I set the chipset before installing the guest has been working fine, though it is not finding my custom PCI device model, but that's a different problem.