Patch "arm64: kernel: Init MDCR_EL2 even in the absence of a PMU" has been added to the 4.4-stable tree

Patch "arm64: kernel: Init MDCR_EL2 even in the absence of a PMU" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    arm64: kernel: Init MDCR_EL2 even in the absence of a PMU

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm64-kernel-init-mdcr_el2-even-in-the-absence-of-a-pmu.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 850540351bb1a4fa5f192e5ce55b89928cc57f42 Mon Sep 17 00:00:00 2001
From: Marc Zyngier <marc.zyngier@arm.com>
Date: Mon, 17 Oct 2016 13:47:34 +0100
Subject: arm64: kernel: Init MDCR_EL2 even in the absence of a PMU

From: Marc Zyngier <marc.zyngier@arm.com>

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@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 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
@@ -518,8 +518,9 @@ 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


Patches currently in stable-queue which might be from marc.zyngier@arm.com are

queue-4.4/arm64-kernel-init-mdcr_el2-even-in-the-absence-of-a-pmu.patch
queue-4.4/irqchip-gicv3-handle-loop-timeout-proper.patch
queue-4.4/irqchip-gic-v3-its-fix-entry-size-mask-for-gits_baser.patch