On Fri, Dec 01, 2017 at 05:31:20PM +0000, Russell King - ARM Linux wrote: > On Fri, Dec 01, 2017 at 06:14:58PM +0100, Peter Zijlstra wrote: > > Well, PREEMPT cares about that too. > > Preempt may care, but it's the hit you take to use neon in the kernel. > The neon register set shares with the FPU, so preempting during that > path means that the normal FPU register saving would corrupt the > already saved user FPU context - and even worse would result in the > kernel's crypto function register contents being leaked to userspace. Same thing on x86. > If you care about preempt deeply, the only solution is to avoid using > kernel mode neon. Not quite, you can write the code such that it drops out of neon mode regularly to allow preemption. So setup a crypto block, enter neon, transform the block, drop out of neon, rinse repeat. -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
