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[PATCH 3.16.y-ckt 005/104] arm64: head.S: initialise mdcr_el2 in el2_setup

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3.16.7-ckt19 -stable review patch.  If anyone has any objections, please let me know.

------------------

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

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@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 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 1cd11e73058f..a089ce8d52b3 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -315,6 +315,11 @@ CPU_LE(	movk	x0, #0x30d0, lsl #16	)	// Clear EE and E0E on LE systems
 	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
 
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[3.16.y-ckt stable] Linux 3.16.7-ckt19 stable review Luis Henriques <luis.henriques@canonical.com> - 2015-10-26 15:30 +0100
  [PATCH 3.16.y-ckt 005/104] arm64: head.S: initialise mdcr_el2 in el2_setup Luis Henriques <luis.henriques@canonical.com> - 2015-10-26 15:30 +0100
  [PATCH 3.16.y-ckt 038/104] usb: xhci: Clear XHCI_STATE_DYING on start Luis Henriques <luis.henriques@canonical.com> - 2015-10-26 15:30 +0100
  [PATCH 3.16.y-ckt 006/104] kvm: don't try to register to KVM_FAST_MMIO_BUS for non mmio eventfd Luis Henriques <luis.henriques@canonical.com> - 2015-10-26 15:30 +0100
  [PATCH 3.16.y-ckt 027/104] drm/vmwgfx: Fix up user_dmabuf refcounting Luis Henriques <luis.henriques@canonical.com> - 2015-10-26 15:30 +0100
  [PATCH 3.16.y-ckt 001/104] ARM: 8429/1: disable GCC SRA optimization Luis Henriques <luis.henriques@canonical.com> - 2015-10-26 15:30 +0100
  [PATCH 3.16.y-ckt 015/104] arm64: errata: add module build workaround for erratum #843419 Luis Henriques <luis.henriques@canonical.com> - 2015-10-26 15:30 +0100
  [PATCH 3.16.y-ckt 029/104] Btrfs: fix read corruption of compressed and shared extents Luis Henriques <luis.henriques@canonical.com> - 2015-10-26 15:30 +0100
  [PATCH 3.16.y-ckt 105/107] KEYS: Fix race between key destruction and finding a keyring by name Luis Henriques <luis.henriques@canonical.com> - 2015-10-26 20:10 +0100
  [PATCH 3.16.y-ckt 107/107] KEYS: Don't permit request_key() to construct a new keyring Luis Henriques <luis.henriques@canonical.com> - 2015-10-26 20:10 +0100
  Re: [3.16.y-ckt stable] Linux 3.16.7-ckt19 stable review Luis Henriques <luis.henriques@canonical.com> - 2015-10-26 20:10 +0100
    Re: [3.16.y-ckt stable] Linux 3.16.7-ckt19 stable review Luis Henriques <luis.henriques@canonical.com> - 2015-10-28 18:00 +0100
  [PATCH 3.16.y-ckt 106/107] KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring Luis Henriques <luis.henriques@canonical.com> - 2015-10-26 20:10 +0100
  [PATCH 3.16.y-ckt 108/108] Btrfs: update fix for read corruption of compressed and shared extents Luis Henriques <luis.henriques@canonical.com> - 2015-10-28 18:00 +0100

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