DMA and IRQ on guests

[sunborn]

I know VMware ESXi is not really meant to do this but...

I have a MS-DOS (or FreeDOS) or even Windows 95 guest VM that I have with an audiocard on PCI passthrough. This audiocard driver works by trapping DMA and IRQ and passing it to the real IRQ of 10 (0xA).

Something is going wrong. Just installing the driver corrupts the windows 95 install on protected memory faults (I think). The MS-DOS 6.22 install loads the TSR (terminate and stay resident) driver, but the sound just doesn't come out.

I even bought a different soundcard from the same era in case it was a driver issue. Different card, different OEM, different driver. Same problem.

I assume it is a DMA or IRQ issue. How do I fix this?

I set VMkernel.Boot.iovDisableIR=TRUE to try and fix the IRQ issue, but I really think it could be a DMA thing too. Is the DMA going to be an issue?

How do I get the BIOS to free up IRQ 7? or really any IRQ? The Microsoft Diagnostics Program says that all IRQ are either used or reserved (i.e. none available).

System is a Supermicro X10DRi running ESXi 6.5.0 Build 8294253 (U2, I think). Is there some magic flag somewhere that just makes this work?

[sunborn]

From the dearth of free support here, I am considering paying per-incident tech support. Would this be covered in a per-incident? What is the probability that they can fix this for me?

[daphnissov]

What is the probability that they can fix this for me?

Probably slim to none. Look, the issue is you're wanting to do things that shouldn't be done that aren't supported with ancient things. You said it right from the outset:

I know VMware ESXi is not really meant to do this but...

so don't do it. It really sounds like what you need/want to do is a good reason to have some old physical gear, but not try and fit this square peg into the round hole of virtualization. Stuff like this never works out very well.

[sunborn]

Do you think that Teradici zero client would work for MS-DOS? I could add a virtual soundblaster and driver for DOS and the zero PCoIP protocol does sound.

[daphnissov]

I don't if it will or won't, I'd just say I *highly* doubt you're going to get any zero client to work with MS-DOS. I think your best route is as I suggested:  Do this on physical gear.

[sunborn · Accepted solution]

So I got the device working under Windows 95, but not under real mode DOS. I guess that it is a driver issue and not a ESXi problem.