On Thu, Apr 09, 2020 at 05:59:56PM +0200, Peter Zijlstra wrote: > On Thu, Apr 02, 2020 at 04:13:08PM +0200, Peter Zijlstra wrote: > > On Thu, Apr 02, 2020 at 09:33:54AM +0200, Christian König wrote: > > > > yes, using the floating point calculations in the display code has been a > > > source of numerous problems and confusion in the past. > > > > > > The calls to kernel_fpu_begin() and kernel_fpu_end() are hidden behind the > > > DC_FP_START() and DC_FP_END() macros which are supposed to hide the > > > architecture depend handling for x86 and PPC64. > > > > > > This originated from the graphics block integrated into AMD CPU (where we > > > knew which fp unit we had), but as far as I know is now also used for > > > dedicated AMD GPUs as well. > > > > > > I'm not really a fan of this either, but so far we weren't able to convince > > > the hardware engineers to not use floating point calculations for the > > > display stuff. > 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? 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. 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) ? _______________________________________________ amd-gfx mailing list amd-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/amd-gfx
