On Thu, Dec 07, 2017 at 03:47:43PM +0000, Ard Biesheuvel wrote: > On 7 December 2017 at 14:50, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > > On 7 December 2017 at 14:39, Dave Martin <Dave.Martin@xxxxxxx> wrote: > >> On Wed, Dec 06, 2017 at 07:43:37PM +0000, Ard Biesheuvel wrote: [...] > >>> + .macro if_will_cond_yield_neon > >>> +#ifdef CONFIG_PREEMPT > >>> + get_thread_info x0 > >>> + ldr w1, [x0, #TSK_TI_PREEMPT] > >>> + ldr x0, [x0, #TSK_TI_FLAGS] > >>> + cmp w1, #1 // == PREEMPT_OFFSET > >> > >> Can we at least drop a BUILD_BUG_ON() somewhere to check this? > >> > >> Maybe in kernel_neon_begin() since this is intimately kernel-mode NEON > >> related. > >> > > > > Sure. > > > > I only just understood your asm-offsets remark earlier. I wasn't aware > that it allows exposing random constants as well (although it is > fairly obvious now that I do). So I will expose PREEMPT_OFFSET rather > than open code it [...] OK, yes, this works for any C expression that is compiletime-constant but requires evaluation that the assembler doesn't understand. Cheers ---Dave
