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: Jiri Slaby <jslaby@suse.cz>

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 7090c126797cb27e3db102e830d5de72c14c3310..aca41b06dc7a759f194306227f9f57255c321bf0 100644 (file)
--- 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