KVM: MIPS: Use CP0_BadInstr[P] for emulation

When exiting from the guest, store the values of the CP0_BadInstr and
CP0_BadInstrP registers if they exist, which contain the encodings of
the instructions which caused the last synchronous exception.

When the instruction is needed for emulation, kvm_get_badinstr() and
kvm_get_badinstrp() are used instead of calling kvm_get_inst() directly,
to decide whether to read the saved CP0_BadInstr/CP0_BadInstrP registers
(if they exist), or read the instruction from memory (if not).

The use of these registers should be more robust than using
kvm_get_inst(), as it actually gives the instruction encoding seen by
the hardware rather than relying on user accessors after the fact, which
can be fooled by incoherent icache or a racing code modification. It
will also work with VZ, where the guest virtual memory isn't directly
accessible by the host with user accessors.

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, 1 insertions, 1 deletions

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 29afd96069ef..b8f04070bf39 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -1471,7 +1471,7 @@ int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
 		if (cause & CAUSEF_BD)
 			opc += 1;
 		inst = 0;
-		kvm_get_inst(opc, vcpu, &inst);
+		kvm_get_badinstr(opc, vcpu, &inst);
 		kvm_err("Exception Code: %d, not yet handled, @ PC: %p, inst: 0x%08x  BadVaddr: %#lx Status: %#lx\n",
 			exccode, opc, inst, badvaddr,
 			kvm_read_c0_guest_status(vcpu->arch.cop0));