On 26/11/13 14:41, Andre Przywara wrote:
On 11/21/2013 09:59 AM, Marc Zyngier wrote:
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...
Under what circumstances would native Linux use the virtual timers? When VIRT_EXT is not defined?
Yes. In general, when the kernel is not entered in HYP mode.
M.
Regards, Andre.
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: