arm64: head.S: initialise mdcr_el2 in el2_setup

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.

Cc: <stable@vger.kernel.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index a055be6..90d09ed 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -523,6 +523,11 @@ 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