Enable trapping of the debug registers, preventing the guests to
mess with the host state (and allowing guests to use the debug
infrastructure as well).

Reviewed-by: Anup Patel <anup.pa...@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyng...@arm.com>
---
 arch/arm64/kvm/hyp.S | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index 73ec5c4..72ed0bf8 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -777,6 +777,14 @@ __kvm_hyp_code_start:
        mrs     x2, mdcr_el2
        and     x2, x2, #MDCR_EL2_HPMN_MASK
        orr     x2, x2, #(MDCR_EL2_TPM | MDCR_EL2_TPMCR)
+       orr     x2, x2, #(MDCR_EL2_TDRA | MDCR_EL2_TDOSA)
+
+       // Check for KVM_ARM64_DEBUG_DIRTY, and set to debug to trap
+       // if not dirty.
+       ldr     x3, [x0, #VCPU_DEBUG_FLAGS]
+       tbnz    x3, #KVM_ARM64_DEBUG_DIRTY_SHIFT, 1f
+       orr     x2, x2,  #MDCR_EL2_TDA
+1:
        msr     mdcr_el2, x2
 .endm
 
-- 
1.8.3.4

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