[Barrelfish-users] Bug fix related to FPU context switch on LRPC path for x86_64

[Andrei Poenaru]

Dear all,

While working on context switching I found a bug regarding the FPU context
switching on the LRPC path: no FPU switching is performed on that path.

When 2 domains (using the FPU) communicate via LRPC the data stored in the
registers is not correctly preserved. I was able to derive a test starting
from 'lrpc_bench'.

In order to fix the issue, I implemented in assembly, on the LRPC path, the
same logic as in 'fpu_lazy_top' (function called during a context switch on
the normal kernel path).

The test and the proposed fix can be found in the attached patch.

Best regards,
Andrei
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