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

[Timothy Roscoe]

Dear Andrei,

Many thanks - that's great.  Adam: could you have a look at this?

Cheers,

 -- Mothy

At Sat, 14 Jan 2017 14:24:34 +0100, Andrei Poenaru <poenarua at ethz.ch> wrote:
> 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
>