MIPS: KVM: Fix CACHE immediate offset sign extension

The immediate field of the CACHE instruction is signed, so ensure that
it gets sign extended by casting it to an int16_t rather than just
masking the low 16 bits.

Fixes: e685c689f3a8 ("KVM/MIPS32: Privileged instruction/target branch emulation.")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Cc: <stable@vger.kernel.org> # 3.10.x-
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
index d5fa3eaf39a106546f52d82ec3e5391302ef8dec..41b1b090f56f6b73afc50240318634a4988ef427 100644 (file)
--- a/arch/mips/kvm/emulate.c
+++ b/arch/mips/kvm/emulate.c
@@ -1581,7 +1581,7 @@ enum emulation_result kvm_mips_emulate_cache(uint32_t inst, uint32_t *opc,
 
        base = (inst >> 21) & 0x1f;
        op_inst = (inst >> 16) & 0x1f;
-       offset = inst & 0xffff;
+       offset = (int16_t)inst;
        cache = (inst >> 16) & 0x3;
        op = (inst >> 18) & 0x7;