Before switching to non-secure, make sure that CNTVOFF is set to zero on all CPUs. Otherwise, kernel running in non-secure without HYP enabled (hence using virtual timers) may observe timers that are not synchronized, effectively seeing time going backward...
Signed-off-by: Marc Zyngier marc.zyngier@arm.com --- arch/arm/cpu/armv7/nonsec_virt.S | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/arch/arm/cpu/armv7/nonsec_virt.S b/arch/arm/cpu/armv7/nonsec_virt.S index 648066f..bbacbce 100644 --- a/arch/arm/cpu/armv7/nonsec_virt.S +++ b/arch/arm/cpu/armv7/nonsec_virt.S @@ -53,7 +53,14 @@ _secure_monitor: mrceq p15, 0, r0, c12, c0, 1 @ get MVBAR value mcreq p15, 4, r0, c12, c0, 0 @ write HVBAR #endif + bne 1f
+ @ Reset CNTVOFF to 0 before leaving monitor mode + mrc p15, 0, r0, c0, c1, 1 @ read ID_PFR1 + ands r0, r0, #CPUID_ARM_GENTIMER_MASK @ test arch timer bits + movne r0, #0 + mcrrne p15, 4, r0, r0, c14 @ Reset CNTVOFF to zero +1: movs pc, lr @ return to non-secure SVC
_hyp_trap: