target/riscv: fix endless translation loop on big endian systems

target/riscv: fix endless translation loop on big endian systems

On big endian systems, pte and updated_pte hold big endian host data
while pte_pa points to little endian target data. This means the branch
at cpu_helper.c:1669 will be always satisfied and restart translation,
causing an endless translation loop.

The correctness of this patch can be deduced by:

old_pte will hold value either from cpu_to_le32/64(pte) or
cpu_to_le32/64(updated_pte), both of wich is litte endian. After that,
an in-place conversion by le32/64_to_cpu(old_pte) ensures that old_pte
now is in native endian, same with pte. Therefore, the endianness of the
both side of if (old_pte != pte) is correct.

Signed-off-by: Ziqiao Kong <ziqiaokong@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20250415080254.3667878-2-ziqiaokong@gmail.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Cc: qemu-stable@nongnu.org