KVM: arm64: guest debug, define API headers

This commit defines the API headers for guest debugging. There are two
architecture specific debug structures:

  - kvm_guest_debug_arch, allows us to pass in HW debug registers
  - kvm_debug_exit_arch, signals exception and possible faulting address

The type of debugging being used is controlled by the architecture
specific control bits of the kvm_guest_debug->control flags in the ioctl
structure.
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/include/uapi/asm/kvm.h

@@ -100,12 +100,39 @@ struct kvm_sregs {
 struct kvm_fpu {
 };
 
+/*
+ * See v8 ARM ARM D7.3: Debug Registers
+ *
+ * The architectural limit is 16 debug registers of each type although
+ * in practice there are usually less (see ID_AA64DFR0_EL1).
+ *
+ * Although the control registers are architecturally defined as 32
+ * bits wide we use a 64 bit structure here to keep parity with
+ * KVM_GET/SET_ONE_REG behaviour which treats all system registers as
+ * 64 bit values. It also allows for the possibility of the
+ * architecture expanding the control registers without having to
+ * change the userspace ABI.
+ */
+#define KVM_ARM_MAX_DBG_REGS 16
 struct kvm_guest_debug_arch {
+	__u64 dbg_bcr[KVM_ARM_MAX_DBG_REGS];
+	__u64 dbg_bvr[KVM_ARM_MAX_DBG_REGS];
+	__u64 dbg_wcr[KVM_ARM_MAX_DBG_REGS];
+	__u64 dbg_wvr[KVM_ARM_MAX_DBG_REGS];
 };
 
 struct kvm_debug_exit_arch {
+	__u32 hsr;
+	__u64 far;	/* used for watchpoints */
 };
 
+/*
+ * Architecture specific defines for kvm_guest_debug->control
+ */
+
+#define KVM_GUESTDBG_USE_SW_BP		(1 << 16)
+#define KVM_GUESTDBG_USE_HW		(1 << 17)
+
 struct kvm_sync_regs {
 };