linux-kernel - [PATCH 3.12 40/84] arm64: head.S: initialise mdcr_el2 in el2

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Message-Id: <3ebb37283c93282592beba3f01e46c8f8371dee8.1443792303.git.jslaby@suse.cz>
Date:	Fri,  2 Oct 2015 15:24:45 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Will Deacon <will.deacon@....com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 40/84] arm64: head.S: initialise mdcr_el2 in el2_setup

From: Will Deacon <will.deacon@....com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit d10bcd473301888f957ec4b6b12aa3621be78d59 upstream.

When entering the kernel at EL2, we fail to initialise the MDCR_EL2
register which controls debug access and PMU capabilities at EL1.

This patch ensures that the register is initialised so that all traps
are disabled and all the PMU counters are available to the host. When a
guest is scheduled, KVM takes care to configure trapping appropriately.

Acked-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/arm64/kernel/head.S | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 7090c126797c..aca41b06dc7a 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -192,6 +192,11 @@ ENTRY(el2_setup)
 	msr	hstr_el2, xzr			// Disable CP15 traps to EL2
 #endif
 
+	/* EL2 debug */
+	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
+
 	/* Stage-2 translation */
 	msr	vttbr_el2, xzr
 
-- 
2.6.0

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