Re: [PATCH v2 1/5] nds32: nds32 FPU port
From: Arnd Bergmann
Date: Fri Oct 12 2018 - 05:22:59 EST
On Fri, Oct 12, 2018 at 10:52 AM Vincent Chen <vincentc@xxxxxxxxxxxxx> wrote:
> On Thu, Oct 11, 2018 at 03:30:30PM +0800, Arnd Bergmann wrote:
> > On Thu, Oct 11, 2018 at 4:56 AM Vincent Chen <vincentc@xxxxxxxxxxxxx> wrote:
> > There was a long discussion on RISC-V about what happens when
> > FPU support is enabled or disabled, you may have seen that as well.
> > Can you confirm that:
> > a) A kernel with FPU support enabled running on a CPU without an FPU
> > will behave the same as a kernel without FPU support, and in particular
> > not crash while trying to access the FPU
> > b) A kernel with FPU support disabled running on a CPU with an FPU
> > prevents user space from accessing the FPU, to avoid corrupting
> > FPU registers during a task switch when a process accidentally contains
> > FPU access
> In this patch user program will be terminated when accessing FPU register
> if the FPU support is disabled on kernel. Hence, condition b) is promised.
> Condition a) is unsupported in this patch. I will add this support in
> the next version patch.
Ok, sounds good, thanks