Subject: Re: [PATCH 02/29] powerpc/rtas: prevent suspend-related sys_rtas use on LE

From: Nathan Lynch <[email-masked]>
Date: Fri, 30 Oct 2020 07:10:24 -0500

Andrew Donnellan <[email-masked]> writes:
> On 30/10/20 12:17 pm, Nathan Lynch wrote:
>> While drmgr has had work in some areas to make its RTAS syscall
>> interactions endian-neutral, its code for performing partition
>> migration via the syscall has never worked on LE. While it is able to
>> complete ibm,suspend-me successfully, it crashes when attempting the
>> subsequent ibm,update-nodes call.
>> 
>> drmgr is the only known (or plausible) user of these ibm,suspend-me,
>> ibm,update-nodes, and ibm,update-properties, so allow them only in
>> big-endian configurations.
>
> And there's a zero chance that drmgr will ever be fixed on LE?

It's always used the sysfs interface on LE, and the only way to provoke
it to attempt the syscalls is by doing something like this before
running the migration:

# echo 0 > /tmp/fake_api_version
# mount -o bind,ro /tmp/fake_api_version /sys/kernel/mobility/api_version

So I'm not aware of any circumstance that would actually motivate
someone to make it work on LE. I'd say it's more likely that drmgr will
drop its support for using the syscall altogether.