Am 09.04.20 um 19:09 schrieb Peter Zijlstra:
On Thu, Apr 09, 2020 at 05:59:56PM +0200, Peter Zijlstra wrote:
[SNIP]
I'll need another approach, let me consider.
Christian; it says these files are generated, does that generator know
which functions are wholly in FPU context and which are not?
Well that "generator" is still a human being :)
It's just that the formulae for the calculation come from the hardware
team and we are not able to easily transcript them to fixed point
calculations.
My current thinking is that if I annotate all functions that are wholly
inside kernel_fpu_start() with an __fpu function attribute, then I can
verify that any call from regular text to fpu text only happens inside
kernel_fpu_begin()/end(). And I can ensure that all !__fpu annotation
fuctions only contain !fpu instructions.
Yeah, that sounds like a good idea to me and should be easily doable.
Can that generator add the __fpu function attribute or is that something
that would need to be done manually (which seems like it would be
painful, since it is quite a bit of code) ?
We are currently in the process of moving all the stuff which requires
floating point into a single C file(s) and then make sure that we only
call those within kernel_fpu_begin()/end() blocks.
Annotating those function with __fpu or even saying to gcc that all code
of those files should go into a special text.fpu segment shouldn't be
much of a problem.
Regards,
Christian.
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