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Re: [PATCH v5 2/2] target/xtensa: Use semihosting/syscalls.h
From: |
Alex Bennée |
Subject: |
Re: [PATCH v5 2/2] target/xtensa: Use semihosting/syscalls.h |
Date: |
Wed, 29 Jun 2022 09:06:53 +0100 |
User-agent: |
mu4e 1.7.27; emacs 28.1.50 |
Richard Henderson <richard.henderson@linaro.org> writes:
> On 6/28/22 19:08, Max Filippov wrote:
>> On Tue, Jun 28, 2022 at 4:43 AM Richard Henderson
>> <richard.henderson@linaro.org> wrote:
>>>
>>> This separates guest file descriptors from host file descriptors,
>>> and utilizes shared infrastructure for integration with gdbstub.
>>> Remove the xtensa custom console handing and rely on the
>>> generic -semihosting-config handling of chardevs.
>>>
>>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>>> ---
>>> target/xtensa/cpu.h | 1 -
>>> hw/xtensa/sim.c | 3 -
>>> target/xtensa/xtensa-semi.c | 226 ++++++++----------------------------
>>> 3 files changed, 50 insertions(+), 180 deletions(-)
>>>
>>> diff --git a/target/xtensa/cpu.h b/target/xtensa/cpu.h
>>> index ea66895e7f..99ac3efd71 100644
>>> --- a/target/xtensa/cpu.h
>>> +++ b/target/xtensa/cpu.h
>>> @@ -612,7 +612,6 @@ void xtensa_translate_init(void);
>>> void **xtensa_get_regfile_by_name(const char *name, int entries, int
>>> bits);
>>> void xtensa_breakpoint_handler(CPUState *cs);
>>> void xtensa_register_core(XtensaConfigList *node);
>>> -void xtensa_sim_open_console(Chardev *chr);
>>> void check_interrupts(CPUXtensaState *s);
>>> void xtensa_irq_init(CPUXtensaState *env);
>>> qemu_irq *xtensa_get_extints(CPUXtensaState *env);
>>> diff --git a/hw/xtensa/sim.c b/hw/xtensa/sim.c
>>> index 946c71cb5b..5cca6a170e 100644
>>> --- a/hw/xtensa/sim.c
>>> +++ b/hw/xtensa/sim.c
>>> @@ -87,9 +87,6 @@ XtensaCPU *xtensa_sim_common_init(MachineState *machine)
>>> xtensa_create_memory_regions(&sysram, "xtensa.sysram",
>>> get_system_memory());
>>> }
>>> - if (serial_hd(0)) {
>>> - xtensa_sim_open_console(serial_hd(0));
>>> - }
>> I've noticed that with this change '-serial stdio' and its variants
>> are still
>> accepted in the command line, but now they do nothing.
>
> Pardon? They certainly will do something, via writes to the serial hardware.
>
>
>> This quiet
>> change of behavior is unfortunate. I wonder if it would be acceptable
>> to map the '-serial stdio' option in the presence of '-semihosting' to
>> something like '-chardev stdio,id=id1 -semihosting-config chardev=id1'?
>
> I dunno. I'm wary of having xtensa be unique here. Alex, thoughts?
Is semihosting *the* serial hardware for xtensa-sim or is it overriding
another serial interface? I'm wary of adding more magical behaviour for
-serial as it can be confusing enough already what actually gets routed
to it if not doing everything explicitly.
>
>>> + if (get_user_u32(tv_sec, regs[5]) ||
>>> + get_user_u32(tv_usec, regs[5])) {
>> get_user_u32(tv_usec, regs[5] + 4)?
>
> Oops, yes.
>
>>> - regs[2] = select(fd + 1,
>>> - rq == SELECT_ONE_READ ? &fdset : NULL,
>>> - rq == SELECT_ONE_WRITE ? &fdset : NULL,
>>> - rq == SELECT_ONE_EXCEPT ? &fdset : NULL,
>>> - target_tv ? &tv : NULL);
>>> - regs[3] = errno_h2g(errno);
>>> + /* Poll timeout is in milliseconds; overflow to infinity.
>>> */
>>> + msec = tv_sec * 1000ull + DIV_ROUND_UP(tv_usec, 1000ull);
>>> + timeout = msec <= INT32_MAX ? msec : -1;
>>> + } else {
>>> + timeout = -1;
>>> }
>>> +
>>> + switch (regs[4]) {
>>> + case SELECT_ONE_READ:
>>> + events = G_IO_IN;
>>> + break;
>>> + case SELECT_ONE_WRITE:
>>> + events = G_IO_OUT;
>>> + break;
>>> + case SELECT_ONE_EXCEPT:
>>> + events = G_IO_PRI;
>>> + break;
>>> + default:
>>> + xtensa_cb(cs, -1, EINVAL);
>> This doesn't match what there used to be: it was possible to call
>> select_one with rq other than SELECT_ONE_* and that would've
>> passed NULL for all fd sets in the select invocation turning it into
>> a sleep. It would return 0 after the timeout.
>
> Hmm. Is there any documentation of what it was *supposed* to do?
> Passing rq == 0xdeadbeef and expecting a specific behaviour seems odd.
>
>
> r~
--
Alex Bennée
Re: [PATCH v5 0/2] target/xtensa: semihosting cleanup, Max Filippov, 2022/06/28