From 850540351bb1a4fa5f192e5ce55b89928cc57f42 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Mon, 17 Oct 2016 13:47:34 +0100 Subject: [PATCH] arm64: kernel: Init MDCR_EL2 even in the absence of a PMU 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 Cc: Will Deacon Cc: Signed-off-by: Marc Zyngier Signed-off-by: Will Deacon --- arch/arm64/kernel/head.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 427f6d3f084c..332e33193ccf 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -586,8 +586,9 @@ CPU_LE( movk x0, #0x30d0, lsl #16 ) // Clear EE and E0E on LE systems 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 -- 2.20.1