KVM: MIPS: Drop dubious EntryHi optimisation

There exists a slightly dubious optimisation in the implementation of
the MIPS KVM EntryHi emulation which skips TLB invalidation if the
EntryHi points to an address in the guest KSeg0 region, intended to
catch guest TLB invalidations where the ASID is almost immediately
restored to the previous value.

Now that we perform lazy host ASID regeneration for guest user mode when
the guest ASID changes we should be able to drop the optimisation
without a significant impact (only the extra TLB refills for the small
amount of code while the TLB is being invalidated).

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

diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
index 8dc9e64346e61d6a28d9dff91d4fc5351e4de35c..4db4c03708590f3030bdf84d87264ad2a79f6bc4 100644 (file)
--- a/arch/mips/kvm/emulate.c
+++ b/arch/mips/kvm/emulate.c
@@ -1162,8 +1162,7 @@ enum emulation_result kvm_mips_emulate_CP0(union mips_instruction inst,
                        } else if (rd == MIPS_CP0_TLB_HI && sel == 0) {
                                u32 nasid =
                                        vcpu->arch.gprs[rt] & KVM_ENTRYHI_ASID;
-                               if ((KSEGX(vcpu->arch.gprs[rt]) != CKSEG0) &&
-                                   ((kvm_read_c0_guest_entryhi(cop0) &
+                               if (((kvm_read_c0_guest_entryhi(cop0) &
                                      KVM_ENTRYHI_ASID) != nasid)) {
                                        trace_kvm_asid_change(vcpu,
                                                kvm_read_c0_guest_entryhi(cop0)