Resizable BAR Support Being Prepared For Coreboot

[Developer12]

The linked follow-up patch points to google/brya (agah variant). https://chromeunboxed.com/12th-gen-i...s-development/ claims it's a Chromebook. "secret device they use internally", really?

There's no indication that they're implementing this support for that upcoming chromebook. Google also runs coreboot on their servers.

At any rate, I'm not talking about the platform. I'm talking about whatever this mystery PCIe device is that google is building with resizable BAR support. Last I checked, google don't make GPUs, so it's probably some proprietary TPU.

[Developer12]

The linked follow-up patch points to google/brya (agah variant). https://chromeunboxed.com/12th-gen-i...s-development/ claims it's a Chromebook. "secret device they use internally", really?

I'm not talking about the platform. I'm talking about whatever device needs resizable bar. Until intel's recent announcement of resizable bar support, the logical conclusion would be some internal google TPU unit that wouldn't be accessible to anyone else on earth.

[avph]

There's no indication that they're implementing this support for that upcoming chromebook. Google also runs coreboot on their servers.

At any rate, I'm not talking about the platform. I'm talking about whatever this mystery PCIe device is that google is building with resizable BAR support. Last I checked, google don't make GPUs, so it's probably some proprietary TPU.

You're wrong. https://review.coreboot.org/c/coreboot/+/61217 Clearly shows it's used on a Intel Alderlake based chromeos device.
Coreboot has no google server support in the tree at the moment, so IDK where you get that information. I think, although I don't know for sure that Google is looking into coreboot server support, but that's all.

[Developer12]

You're wrong. https://review.coreboot.org/c/coreboot/+/61217 Clearly shows it's used on a Intel Alderlake based chromeos device.
Coreboot has no google server support in the tree at the moment, so IDK where you get that information. I think, although I don't know for sure that Google is looking into coreboot server support, but that's all.

All of google's servers run coreboot and have for years. We know this from the many, many talks that Ron Minich has given on his work at google and what they've published through OCP. The servers are published in coreboot in the form of the AMD reference platforms they're based on.

Google isn't generous enough to publish code that would reveal the exact configuration and wiring of their production machines. With the goal of a 10x improvement every generation (at least back when they acquired Motorola's chipmaking division) the specifics of the design are the result of hard-won effort and are kept under wraps. Even something simple like the PCIe topology would be very revealing.

Edit: hell, this was nearly five years ago and despite the title by then the use of coreboot was well underway https://www.reddit.com/r/linux/comme...h_coreboot_on/

[avph]

All of google's servers run coreboot and have for years. We know this from the many, many talks that Ron Minich has given on his work at google and what they've published through OCP. The servers are published in coreboot in the form of the AMD reference platforms they're based on.

Google isn't generous enough to publish code that would reveal the exact configuration and wiring of their production machines. With the goal of a 10x improvement every generation (at least back when they acquired Motorola's chipmaking division) the specifics of the design are the result of hard-won effort and are kept under wraps. Even something simple like the PCIe topology would be very revealing.

Edit: hell, this was nearly five years ago and despite the title by then the use of coreboot was well underway https://www.reddit.com/r/linux/comme...h_coreboot_on/

I think you are confused. Google (and other big companies) seem to use and like LinuxBoot a lot, which is putting Linux + u-root inside boot flash. Coreboot is a different thing and while it's gaining traction on server platforms with OCP, it's not yet widely deployed. Coreboot (basic hardware init) and LinuxBoot (Linux as a bootloader) match well but the projects are orthogonal.

There is some work to get oreboot (rust) and not coreboot on AMD servers. That is a still in an early POC state. Not in production afaik.

From that presentation you linked: "While we prefer coreboot-based systems we can use u-root on UEFI-based systems via NERF". Google uses LinuxBoot, so Linux + u-root (go written initramfs/busybox) as a firmware solution in production, I was told. That is not the same coreboot. NERF is about using LinuxBoot inside existing UEFI firmware, while also dramatically trimming down UEFI DXE modules you don't need. The reddit title is just misleading/wrong...

[Developer12]

I think you are confused. Google (and other big companies) seem to use and like LinuxBoot a lot, which is putting Linux + u-root inside boot flash. Coreboot is a different thing and while it's gaining traction on server platforms with OCP, it's not yet widely deployed. Coreboot (basic hardware init) and LinuxBoot (Linux as a bootloader) match well but the projects are orthogonal.

There is some work to get oreboot (rust) and not coreboot on AMD servers. That is a still in an early POC state. Not in production afaik.

From that presentation you linked: "While we prefer coreboot-based systems we can use u-root on UEFI-based systems via NERF". Google uses LinuxBoot, so Linux + u-root (go written initramfs/busybox) as a firmware solution in production, I was told. That is not the same coreboot. NERF is about using LinuxBoot inside existing UEFI firmware, while also dramatically trimming down UEFI DXE modules you don't need. The reddit title is just misleading/wrong...

That presentation is describing an alternative the developed because developing a version of coreboot for off-the-shelf server boards had been painful for many years.

All of the hyperscalars (google, faceboot, etc) have been running coreboot so long (and publishing it through OCP) that there are now companies like oxide are explicitly copying them with the aim of selling it to mid-scale customers. https://github.com/oxidecomputer/coreboot

The VAST majority of google server mainboards are 100% custom machines, not existing Dell or HP machines that NERF is for. Dell and HP machines are rackmount PCs that don't make sense at google's scale, thus OCP and Oxide. It makes no sense to run anything BUT coreboot on custom machines.