KVM: MIPS: Emulate MMIO via TLB miss for EVA

MIPS Enhanced Virtual Addressing (EVA) allows the virtual memory
segments to be rearranged such that the KSeg0/KSeg1 segments are
accessible TLB mapped to user mode, which would trigger a TLB Miss
exception (due to lack of TLB mappings) instead of an Address Error
exception.

Update the TLB Miss handling similar to Address Error handling for guest
MMIO emulation.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org

arch/mips/kvm/trap_emul.c

@@ -175,6 +175,24 @@ static int kvm_trap_emul_handle_tlb_miss(struct kvm_vcpu *vcpu, bool store)
 			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
 			ret = RESUME_HOST;
 		}
+	} else if (KVM_GUEST_KERNEL_MODE(vcpu)
+		   && (KSEGX(badvaddr) == CKSEG0 || KSEGX(badvaddr) == CKSEG1)) {
+		/*
+		 * With EVA we may get a TLB exception instead of an address
+		 * error when the guest performs MMIO to KSeg1 addresses.
+		 */
+		kvm_debug("Emulate %s MMIO space\n",
+			  store ? "Store to" : "Load from");
+		er = kvm_mips_emulate_inst(cause, opc, run, vcpu);
+		if (er == EMULATE_FAIL) {
+			kvm_err("Emulate %s MMIO space failed\n",
+				store ? "Store to" : "Load from");
+			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+			ret = RESUME_HOST;
+		} else {
+			run->exit_reason = KVM_EXIT_MMIO;
+			ret = RESUME_HOST;
+		}
 	} else {
 		kvm_err("Illegal TLB %s fault address , cause %#x, PC: %p, BadVaddr: %#lx\n",
 			store ? "ST" : "LD", cause, opc, badvaddr);