[personal profile] mjg59
Update: Patches to fix this have been posted

There's a story going round that Lenovo have signed an agreement with Microsoft that prevents installing free operating systems. This is sensationalist, untrue and distracts from a genuine problem.

The background is straightforward. Intel platforms allow the storage to be configured in two different ways - "standard" (normal AHCI on SATA systems, normal NVMe on NVMe systems) or "RAID". "RAID" mode is typically just changing the PCI IDs so that the normal drivers won't bind, ensuring that drivers that support the software RAID mode are used. Intel have not submitted any patches to Linux to support the "RAID" mode.

In this specific case, Lenovo's firmware defaults to "RAID" mode and doesn't allow you to change that. Since Linux has no support for the hardware when configured this way, you can't install Linux (distribution installers will boot, but won't find any storage device to install the OS to).

Why would Lenovo do this? I don't know for sure, but it's potentially related to something I've written about before - recent Intel hardware needs special setup for good power management. The storage driver that Microsoft ship doesn't do that setup. The Intel-provided driver does. "RAID" mode prevents the Microsoft driver from binding and forces the user to use the Intel driver, which means they get the correct power management configuration, battery life is better and the machine doesn't melt.

(Why not offer the option to disable it? A user who does would end up with a machine that doesn't boot, and if they managed to figure that out they'd have worse power management. That increases support costs. For a consumer device, why would you want to? The number of people buying these laptops to run anything other than Windows is miniscule)

Things are somewhat obfuscated due to a statement from a Lenovo rep:This system has a Signature Edition of Windows 10 Home installed. It is locked per our agreement with Microsoft. It's unclear what this is meant to mean. Microsoft could be insisting that Signature Edition systems ship in "RAID" mode in order to ensure that users get a good power management experience. Or it could be a misunderstanding regarding UEFI Secure Boot - Microsoft do require that Secure Boot be enabled on all Windows 10 systems, but (a) the user must be able to manage the key database and (b) there are several free operating systems that support UEFI Secure Boot and have appropriate signatures. Neither interpretation indicates that there's a deliberate attempt to prevent users from installing their choice of operating system.

The real problem here is that Intel do very little to ensure that free operating systems work well on their consumer hardware - we still have no information from Intel on how to configure systems to ensure good power management, we have no support for storage devices in "RAID" mode and we have no indication that this is going to get better in future. If Intel had provided that support, this issue would never have occurred. Rather than be angry at Lenovo, let's put pressure on Intel to provide support for their hardware.

Date: 2016-09-24 09:58 pm (UTC)
From: (Anonymous)
A user on Lenovo's forums is running Linux on a SD card on the ISK2 Yoga 900 and said this about the battery life when I quoted your April article about Haswell and Broadwell power management policies:

Matthew's stuff about the PCH power states is interesting. Taking his numbers (which might not be for Skylake) the change in 'idle time' for a 66Wh battery (like in the Yoga 900) between 5W and 8.5W is 13.2 hours and 7.7 hours. Going to go out on a limb here and say that Skylake is probably more efficient.
Any activity on the machine will of course make it use more power.

I've had mine running all week with Ubuntu and off the charger for several days... so sleep works obviously. I'm not noticing any thermal issues which would worry me more. I'm about to start compiling kernels on it so we'll see how that goes... if anything is going to push the thermal management it's that.

I guess what annoys me about all of this is that Lenovo could have just stated this up front; made the patched BIOS available and with the disclaimer it might negatively affect battery performance and cause more thermal throttling. I would be perfectly happy with that... I don't do many eight hour solid sessions on a laptop away from power. YMMV.

What's more annoying is that if you go and read the Intel forums they say go and talk to the Linux kernel developers... and then the kernel developers say Intel doesn't provide the details. Intel have been doing some great work with Linux lately but obviously this isn't one of those areas...


Matthew Garrett

About Matthew

Power management, mobile and firmware developer on Linux. Security developer at Google. Ex-biologist. @mjg59 on Twitter. Content here should not be interpreted as the opinion of my employer.

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