3.16.40-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Marc Zyngier <marc.zyngier@xxxxxxx>
commit 850540351bb1a4fa5f192e5ce55b89928cc57f42 upstream.
Commit f436b2ac90a0 ("arm64: kernel: fix architected PMU registers
unconditional access") made sure we wouldn't access unimplemented
PMU registers, but also left MDCR_EL2 uninitialized in that case,
leading to trap bits being potentially left set.
Make sure we always write something in that register.
Fixes: f436b2ac90a0 ("arm64: kernel: fix architected PMU registers unconditional access")
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
arch/arm64/kernel/head.S | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -322,8 +322,9 @@ CPU_LE( movk x0, #0x30d0, lsl #16 ) // C
b.lt 4f // Skip if no PMU present
mrs x0, pmcr_el0 // Disable debug access traps
ubfx x0, x0, #11, #5 // to EL2 and allow access to
- msr mdcr_el2, x0 // all PMU counters from EL1
4:
+ csel x0, xzr, x0, lt // all PMU counters from EL1
+ msr mdcr_el2, x0 // (if they exist)
/* Stage-2 translation */
msr vttbr_el2, xzr