linux and the ps3 hypervisor

[blitzmagoo]

warning: total noob alert

with yellow dog linux being the "official?" distribution, certain tweeks to the kernel were made for proper function of most, uh, functions, minus most 3d graphic capabiltities.

now with the possibility of having a linux bootloader again without hypervison restrictions, one begins to wonder what sort of tweeks were made. was the ps3 vitualizing the hardware minus 3d gfx, or was it an emulation of an existing ppc environment.

curious to know is this taboo

curious to know if there is much interest in custom respins of ydl with ps3 new found capabilities. say 6.66, lol

[ppietro]

with yellow dog linux being the "official?" distribution, certain tweeks to the kernel were made for proper function of most, uh, functions, minus most 3d graphic capabiltities.

now with the possibility of having a linux bootloader again without hypervison restrictions, one begins to wonder what sort of tweeks were made. was the ps3 vitualizing the hardware minus 3d gfx, or was it an emulation of an existing ppc environment.

Nope - that's not quite right. Let me explain a little - at least the way I understand things.

A Linux kernel normally doesn't contain any 3D routines. Instead, what happens is that you can write additional "kernel module" code that the kernel can dynamically load at boot time. This is a separate piece of code that the kernel loads, and can then access as a kernel function.

Usually these are hardware specific code modules; you connect them to your kernel with the "modprobe" command, after you've installed the code and the hardware. Most 3D Linux graphics drivers have one of these kernel module components.

The reason 3D doesn't work on the PS3 is that the modprobe can't find the hardware it needs to load the kernel module; the actual 3D hardware is hidden by the hypervisor. The Linux kernel doesn't contain the hypervisor - it runs underneath the hypervisor, if you like.

Instead - the way I understand it, the tweaks to the kernel were specifically to include the PowerPC Cell PPE variant and had nothing to do with hypervisor or 3D support. The PPE isn't quite a standard PowerPC architecture - it is somewhat stripped in comparison - specifically with the loss of "out-of-order" processing. Other than that, it's a stock Linux kernel.

The hypervisor would, in fact, make it easier to let YDL run on the PS3. It would take the weird PS3 hardware, and make it look like a regular PC.

Also - don't forget about the Sony Zego. This was basically a rack mounted PS3 that ran YDL. Unlike normal PS3s, this box didn't have hypervisor restrictions on the RSX, and YDL could load the nVidia graphics drivers without any modifications.

So - if you could load Linux from the XMB, I believe you would still have a hypervisor layer - since all PS3 games run under a hypervisor layer - but you would have access to the RSX. If you could get a bootloader to load stock YDL, then I would imagine you would just use the nVidia Linux drivers for 3D video.

Cheers,
Paul

P.S. Contrary to some opinions on other forums and blogs, I don't believe you would change the memory footprint of the PS3 from the XMB either. Linux would still have only 256 megs of system RAM. The additional 256 megs of RSX RAM would still be dedicated to the RSX.

This is because the PS3 doesn't have a unified memory architecture like the 360 - it's a 256/256 split. It's literally physically different types of RAM - RAMBUS vs. GDDR3. You could read and write to the RSX RAM from the Cell - but due to the asymmetrical FlexIO memory controller of the PS3, there's a huge speed penalty. Only the RSX can access full system RAM at high speeds - that's to facilitate texture swapping, I believe.

[trj021782]

I hope what I am posting is not a TAC violation but here goes,

There is a way to dump the hypervisor with a minor hardware mod and some linux software.
I will link you upon request as to avoid pissing off anyone.

[ppietro]

I hope what I am posting is not a TAC violation but here goes,

There is a way to dump the hypervisor with a minor hardware mod and some linux software.
I will link you upon request as to avoid pissing off anyone.

Don't bother - we've discussed the hardware mod extensively before. (If you're discussing Geohot's exploit, that is.)

Currently, most of our users are looking at this mod-free USB exploit to restore Linux functionality to their updated consoles by allowing homebrew:
viewtopic.php?f=19&t=7266&start=450#p39738

(That's where it starts, anyway - we're still discussing)

Cheers,
Paul

[trj021782]

actually I was refering to Xorlosers hard hack wich IS a slightly altered version of Geohot's. It is important to bear in mind that this mod is to remove the restrictions of the Hypervisor - NOT restore linux usablity, that can ONLY be done with firmware - be it custom or official

[ppietro]

actually I was refering to Xorlosers hard hack wich IS a slightly altered version of Geohot's. It is important to bear in mind that this mod is to remove the restrictions of the Hypervisor - NOT restore linux usablity, that can ONLY be done with firmware - be it custom or official

Exactly. We're not as interested in the Geohot hack method - we discussed it quite thoroughly when it came out.

Instead, most of us on the board seem to be preferring the USB method of running unsigned code from the GameOS. The way we understand it, this would allow Linux to run without most hypervisor restrictions, on stock, unmodified firmware(s).

Currently, from what we've seen, they've managed to execute the "Install Other OS" program, and also boot a Linux kernel from TFTP.

They haven't booted a full Linux yet - but they're getting there.

We're documenting this kind of stuff in the thread I referenced above.

Cheers,
Paul