Re: what are the requirements on target/ code for -icount to work correctly?

[Max Filippov]

On Fri, Jun 19, 2020 at 10:05 AM Peter Maydell <peter.maydell@linaro.org> wrote:
> I've just sent a patch that removes the target/arm gen_io_end() calls.
> I had a quick look at sparc, xtensa and ppc, but they were too complicated
> for a quick look to be sufficient :-)

I've checked the xtensa translator. The only gen_io_end() is for
opcodes that end TB when a full instruction is translated, because
they can change active interrupt requests. So it can be removed.
I'll send a patch.

One instance of gen_io_start is for the rsr.ccount opcode that reads
current cycle counter that translates to reading
QEMU_CLOCK_VIRTUAL clock.
Looks like this adds one more case to the
following list:

> As I understand it, the definition of "I/O insn" is anything that can
> either:
>
> - affect the icount deadline (e.g. by setting or removing a
> QEMU_CLOCK_VIRTUAL timer)
>
> - interrupt the current translation block with cpu_loop_exit,
> cpu_restore_state or similar.

-- 
Thanks.
-- Max