32-bit ARM Is Also On The Chopping Block For Ubuntu

[edwaleni]

I wonder what the Android folk think of this ?

[My8th]

For people using current stats of 32bit usage, you'll have to account that Ubuntu 18.04 LTS will be supported till April 2023 which means 32bit will have to be supported for that LTS release for that duration.

[slacka]

One of the major uses for the 32 bit release also is not for 32 bit x86 hardware, but to use inside a VM on a 64 Bit x86 CPU that does not support VT hardware assisted virtualization.You cannot run a 64 bit guest without VT technology on the CPU. But many Intel CPUs did not support VT leaving no way to run a 64 bit guest. !

Maybe, but at least for my company that is not the reason we are running 32 bit guests; it's memory usage. They have hundreds of VMs. In internal tests they found that switching all the guests to x86_64 would require terabytes of additional RAM with little upside. It's too bad the x32 ABI never took of.

[Sniperfox47]

Actually the firmware DOES NOT run on the ARM CPU. It runs on a different RISC that is embed inside the GPU and communicate with the linux kernel running on the ARM through "mailboxes".
Currently (Raspbian Stretch) you can run upstream vanilla kernel (4.14.39 currently) with no necessary blobs, all the blobs remaining inside ThreadX rtos running on the GPU's risc.

(Raspberry Pi, compared to all the other SBC out-there is a really weird architecture.
It's actuall a network of 2 different systems running on 2 different CPUs.
It probably made sens back a the beginning, in an era of awefully closed source firmware on most embed chips : ThreadX takes care of the most thing using blobs running on the GPU, leaving possible to eventually have a possible upstream vanilla kernel on the ARM CPU.
Nowadays, there has been massive effort at opening the firmwares (see the sunxi effrots with Allwinner, see efforts around Rockchip), and it's possible to find lots of SBCs that can run up-to-date upstream kernel, as long as you neglect the current ARM GPU mess)

Raspbian remains 32bits by choice to make a single unified distro that runs from the ARMv6 HF found nowadays in Pi Zero, all the way to the ARMv8 in Pi 3+ /Pi 3/Pi 2 v1.2
(And also they think there isn't much need for a 64bits OS - though opinion on this varry.
Yes, 64bit memory address space is a bit overkill on an embed SoC that cannot physically address more than 1GB (30 pin physical address bus, internally 2bits on the 32bits RAM address space reserved).
But on the other hand the ARMv8 ISA provides more registers, newer opcodes, and can process the large numbers used by cryptography by splitting then into wider 64bit chunks - NOTE: Raspberry Pi's arm happens not to implement lots of the optional crypto hardware, you still need to do a lot of your encryption on the CPU).

There are other distros out there that maintain an ARMv8 kernel (bootcode.bin actually supports looking for one),
there are even a few distros running a ARMv8 userland (mostly lifted from debian aarch64),
specifically for the small speed gain I mentioned above that an ARMv8 isa can bring over the original ARMv6 HF isa.

I never said that the firmware runs on the CPU. I am well aware of how the VC4 architecture is laid out and just how broken it is.

You can read the exact details here: https://github.com/raspberrypi/firmware/issues/550

But the basics are that the VC4 firmware requires a maintained kernel pointer that's in 32 bit format as part of it's ABI to the kernel (because why bother using standard interfaces?) and without an updated VC4 firmware you have to have some kind of compatibility layer sitting between your VC4 driver and the VC4 firmware to get an AArch64 kernel working.

Fedora and Arch both have images for the Raspberry Pi 3 that do this, but it's hacky and not something that works with an off the shelf kernel.

This could have been fixed by Broadcom offering an updated VC4 firmware.

[Faalagorn]

Er. Actually the ARM architecture is where Linux rules supreme. With my excuses to Apple fanboys, it's fair to say that without Linux support, ARM wouldn't nearly be what it is. Yes, Linux was initially conceived as a desktop PC operating system and unfortunately that's the last area that it still has to crack. Bur for pretty much everything else it has long become the go-to OS and dropping it would be the stupidest idea ever.

Nice trolling, pal. How about no.

I have a feeling that leiptrstormr was being sarcastic here