On Fri Sep 16, 2022 at 3:32 PM AEST, Rohan McLure wrote: > Add Kconfig option for enabling clearing of registers on arrival in an > interrupt handler. This reduces the speculation influence of registers > on kernel internals. The option will be consumed by 64-bit systems that > feature speculation and wish to implement this mitigation. > > This patch only introduces the Kconfig option, no actual mitigations. > > The primary overhead of this mitigation lies in an increased number of > registers that must be saved and restored by interrupt handlers on > Book3S systems. Enable by default on Book3E systems, which prior to > this patch eagerly save and restore register state, meaning that the > mitigation when implemented will have minimal overhead. > > Signed-off-by: Rohan McLure <rmcl...@linux.ibm.com>
Thanks for adding this. Maybe I'm being sentimental and we might end up just simplifying code by always doing it... for now I'm happier to have the option. Acked-by: Nicholas Piggin <npig...@gmail.com> > --- > V4 -> V5: New patch > --- > arch/powerpc/Kconfig | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index ef6c83e79c9b..a643ebd83349 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -528,6 +528,15 @@ config HOTPLUG_CPU > > Say N if you are unsure. > > +config INTERRUPT_SANITIZE_REGISTERS > + bool "Clear gprs on interrupt arrival" > + depends on PPC64 && ARCH_HAS_SYSCALL_WRAPPER > + default PPC_BOOK3E_64 > + help > + Reduce the influence of user register state on interrupt handlers and > + syscalls through clearing user state from registers before handling > + the exception. > + > config PPC_QUEUED_SPINLOCKS > bool "Queued spinlocks" if EXPERT > depends on SMP > -- > 2.34.1
