accel/tcg: Call tcg_tb_insert() for one-insn TBs

accel/tcg: Call tcg_tb_insert() for one-insn TBs

Currently one-insn TBs created from I/O memory are not added to
region_trees. Therefore, when they generate exceptions, they are not
handled by cpu_restore_state_from_tb().

For x86 this is not a problem, because x86_restore_state_to_opc() only
restores pc and cc, which already have the correct values if the first
TB instruction causes an exception. However, on several other
architectures, restore_state_to_opc() is not stricly limited to state
restoration and affects some exception-related registers, where guests
can notice incorrect values, for example:

- arm's exception.syndrome;
- hppa's unwind_breg;
- riscv's excp_uw2;
- s390x's int_pgm_ilen.

Fix by always calling tcg_tb_insert(). This may increase the size of
region_trees, but tcg_region_reset_all() clears it once code_gen_buffer
fills up, so it will not grow uncontrollably.

Do not call tb_link_page(), which would add such TBs to the QHT, to
prevent tb_lookup() from finding them. These TBs are single-use, since
subsequent reads from I/O memory may return different values; they are
not removed from code_gen_buffer only in order to keep things simple.

Co-developed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20250116213214.5695-2-iii@linux.ibm.com>