MIPS: Add defs & probing of BadInstr[P] registers

The optional CP0_BadInstr and CP0_BadInstrP registers are written with
the encoding of the instruction that caused a synchronous exception to
occur, and the prior branch instruction if in a delay slot.

These will be useful for instruction emulation in KVM, and especially
for VZ support where reading guest virtual memory is a bit more awkward.

Add CPU option numbers and cpu_has_* definitions to indicate the
presence of each registers, and add code to probe for them using bits in
the CP0_Config3 register.

[ralf@linux-mips.org: resolve merge conflict.]

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13224/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index 6a1a7da..8e54d51 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -714,6 +714,10 @@
 		c->ases |= MIPS_ASE_VZ;
 	if (config3 & MIPS_CONF3_SC)
 		c->options |= MIPS_CPU_SEGMENTS;
+	if (config3 & MIPS_CONF3_BI)
+		c->options |= MIPS_CPU_BADINSTR;
+	if (config3 & MIPS_CONF3_BP)
+		c->options |= MIPS_CPU_BADINSTRP;
 	if (config3 & MIPS_CONF3_MSA)
 		c->ases |= MIPS_ASE_MSA;
 	if (config3 & MIPS_CONF3_PW) {