[vbox-dev] Managing MSI from downstream endpoints

[Vilbig, Ric]

Hi Experts,

I am working on a virtual device model that plugs in to PDM.  The model actually includes a PCI switch and one or more downstream end points of potentially different types.  These end points use MSI for interrupts, so I am using the ICH9 chipset.

Basic initialization goes OK.  I register the device as a PCI switch, VBox enumerates on the downsteam bus, and finds my end point (just one for now, I will add more after I get the first one working).  MSI initialization looks good, the config word in the MSI struct is read as 0x80 and then set to 0x81 (64-bit addressing, no per-vector masking, MSI enabled).  The BIOS and Guest are able to read/write to the MMIO space of the end point.

My problem is when the end point tries to generate an interrupt.  I see the upstream write indicating MSI, and call PDMDevHlpPCISetIrq () to signal the interrupt instead of passing the write up stream.  However, I only have one PPDMDEVINS pDevIns handle, which had been passed to my constructor, and that corresponds to the switch itself.  So when I get down to ich9pciSetIrqInternal(), it's looking at the MSI struct of the switch when it really needs to be looking at the MSI struct of the end point.  And when there are more than one EP, it has to be the correct one.

Presumably I need to have separate device instances for the switch and each downstream end point, so that when I signal an interrupt it knows which end point it's coming from.

My question, then, is how can I allocate additional device handles?  The only way I know how to allocate a device handle is through the CFGM database, with Devices/xyz/0 entries.  But that requires knowing what end points there are in advance, and taking steps to configure CFGM accordingly.  What I really want to do is notice when the bus enumeration finds an end point, and allocate a device instance for it dynamically.  Is there a way to do this?  Or some other way to associate an interrupt request with its source?

BTW, I am using OSE 5.0.16 which I built from the tarball on the virtualbox.org site, running on Ubuntu 14 host with Ubuntu 14 guest (both 64 bits).

_____________________________________________

Ric Vilbig
Mentor Graphics, Emulation Division
46871 Bayside Parkway, Fremont CA, 94538
Phone:  510-354-7360
Mobile: 408-529-2365
email:  ric_vilbig at mentor.com<mailto:ric_vilbig at mentor.com>


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