arm64: head.S: initialise mdcr_el2 in el2_setup

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index c0ff3ce4299e979d11692540a76da4ec5ade5bba..37054116265872ea7c69d6e618bcd8063947f284 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -528,6 +528,11 @@ 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