[Nouveau] Optimus switch corrupts memory on Lenovo T440p

[Nikolay Amiantov]

Hello,
On new Lenovo T440p laptops with new BIOSes (1.16 and further) there is a
memory corruption when trying to disable, and then re-enable, nvidia GPU.
There is a bugreport for bbswitch (
https://github.com/Bumblebee-Project/bbswitch/issues/78), but this problem
shows even when doing disable and re-enable with acpi_call, and nouveau has
dynamic power management support too. I have been trying to investigate
into this problem for some time, and have really no idea what can I try
next. On Windows, this of course works, and I have setted up remote
kernel/ACPI debugging on it, which showed that there is practically no
difference in ACPI calls in Windows from nvidia driver. I've also
discovered correlation of this bug with reserved high memory, which looks
very strange by itself. You can read the whole bug history in this bug
report. I'm posting this to this mailing list to have some help/ideas
regarding this.

Nikolay Amiantov.
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