accel/tcg: Handle get_page_addr_code() returning -1 in hashtable lookups

When we support execution from non-RAM MMIO regions, get_page_addr_code()
will return -1 to indicate that there is no RAM at the requested address.
Handle this in the cpu-exec TB hashtable lookup code, treating it as
"no match found".

Note that the call to get_page_addr_code() in tb_lookup_cmp() needs
no changes -- a return of -1 will already correctly result in the
function returning false.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Reviewed-by: NEmilio G. Cota <cota@braap.org>
Tested-by: NCédric Le Goater <clg@kaod.org>
Message-id: 20180710160013.26559-3-peter.maydell@linaro.org

accel/tcg/cpu-exec.c

@@ -332,6 +332,9 @@ TranslationBlock *tb_htable_lookup(CPUState *cpu, target_ulong pc,
     desc.trace_vcpu_dstate = *cpu->trace_dstate;
     desc.pc = pc;
     phys_pc = get_page_addr_code(desc.env, pc);
+    if (phys_pc == -1) {
+        return NULL;
+    }
     desc.phys_page1 = phys_pc & TARGET_PAGE_MASK;
     h = tb_hash_func(phys_pc, pc, flags, cf_mask, *cpu->trace_dstate);
     return qht_lookup_custom(&tb_ctx.htable, &desc, h, tb_lookup_cmp);