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

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c
index 091553942bcb..3a5484f9aa50 100644
--- a/arch/mips/kvm/trap_emul.c
+++ b/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);