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.zyng...@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
+andsr0, r0, #CPUID_ARM_GENTIMER_MASK@ test arch timer bits
+movne r0, #0
+mcrrne p15, 4, r0, r0, c14 @ Reset CNTVOFF to zero
+1:
movspc, lr @ return to non-secure SVC
_hyp_trap:
--
Jazz is not dead. It just smells funny...
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