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Re: [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, W
From: |
Paolo Bonzini |
Subject: |
Re: [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP) |
Date: |
Tue, 17 Dec 2019 13:22:16 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 |
On 17/12/19 13:14, Alex Bennée wrote:
> [AJB:
>
> So this at least solves the hang of not being able to quit system
> emulation while blocked. However there are two things we still need to
> ensure:
>
> - the PC has not advanced until completion so we can redo the instruction
> - we actually wake up the CPU in console_read
>
> In my testcase console_read never seems to get called. I've tried with
> both an external pipe loopback and using the ringbuf:
>
> qemu-system-aarch64 -M virt --display none -cpu cortex-a57 -kernel
> systest-a64-with-console.axf -semihosting-config
> enable=on,chardev=sh0 -serial mon:stdio -chardev ringbuf,logfile=foo,id=sh0
>
> Signed-off-by: Alex Bennée <address@hidden>
> ---
> include/exec/cpu-all.h | 1 +
> hw/semihosting/console.c | 34 +++++++++++++++++-----------------
> 2 files changed, 18 insertions(+), 17 deletions(-)
>
> diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
> index e96781a4559..093d7a76edd 100644
> --- a/include/exec/cpu-all.h
> +++ b/include/exec/cpu-all.h
> @@ -31,6 +31,7 @@
> #define EXCP_HALTED 0x10003 /* cpu is halted (waiting for external
> event) */
> #define EXCP_YIELD 0x10004 /* cpu wants to yield timeslice to another */
> #define EXCP_ATOMIC 0x10005 /* stop-the-world and emulate atomic */
> +#define EXCP_BLOCKED 0x10006 /* cpu is blocked (semihosting) */
>
> /* some important defines:
> *
> diff --git a/hw/semihosting/console.c b/hw/semihosting/console.c
> index 4db68d62270..bda457a0608 100644
> --- a/hw/semihosting/console.c
> +++ b/hw/semihosting/console.c
> @@ -20,6 +20,7 @@
> #include "hw/semihosting/semihost.h"
> #include "hw/semihosting/console.h"
> #include "exec/gdbstub.h"
> +#include "exec/exec-all.h"
> #include "qemu/log.h"
> #include "chardev/char.h"
> #include <pthread.h>
> @@ -109,50 +110,49 @@ void qemu_semihosting_console_outc(CPUArchState *env,
> target_ulong addr)
>
> typedef struct SemihostingConsole {
> CharBackend backend;
> - pthread_mutex_t mutex;
> - pthread_cond_t cond;
> + CPUState *sleeping_cpu;
> bool got;
> Fifo8 fifo;
> } SemihostingConsole;
>
> -static SemihostingConsole console = {
> - .mutex = PTHREAD_MUTEX_INITIALIZER,
> - .cond = PTHREAD_COND_INITIALIZER
> -};
> +static SemihostingConsole console;
>
> static int console_can_read(void *opaque)
> {
> SemihostingConsole *c = opaque;
> int ret;
> - pthread_mutex_lock(&c->mutex);
> + g_assert(qemu_mutex_iothread_locked());
> ret = (int) fifo8_num_free(&c->fifo);
> - pthread_mutex_unlock(&c->mutex);
> return ret;
> }
>
> static void console_read(void *opaque, const uint8_t *buf, int size)
> {
> SemihostingConsole *c = opaque;
> - pthread_mutex_lock(&c->mutex);
> + g_assert(qemu_mutex_iothread_locked());
> while (size-- && !fifo8_is_full(&c->fifo)) {
> fifo8_push(&c->fifo, *buf++);
> }
> - pthread_cond_broadcast(&c->cond);
> - pthread_mutex_unlock(&c->mutex);
> + if (c->sleeping_cpu) {
> + cpu_resume(c->sleeping_cpu);
> + }
> }
>
> target_ulong qemu_semihosting_console_inc(CPUArchState *env)
> {
> uint8_t ch;
> SemihostingConsole *c = &console;
> - qemu_mutex_unlock_iothread();
> - pthread_mutex_lock(&c->mutex);
> - while (fifo8_is_empty(&c->fifo)) {
> - pthread_cond_wait(&c->cond, &c->mutex);
> + g_assert(qemu_mutex_iothread_locked());
> + g_assert(current_cpu);
> + if (fifo8_is_empty(&c->fifo)) {
> + c->sleeping_cpu = current_cpu;
> + c->sleeping_cpu->stop = true;
> + c->sleeping_cpu->exception_index = EXCP_BLOCKED;
Why do you need to set exception_index to something other than -1 (using
cpu_loop_exit_noexc for example)?
Using ->stop here is a bit weird, since ->stop is usually related to
pause_all_vcpus.
Paolo
- Re: [PATCH] Semihost SYS_READC implementation (v6), Alex Bennée, 2019/12/17
- Re: [PATCH] Semihost SYS_READC implementation (v6), Paolo Bonzini, 2019/12/17
- Re: [PATCH] Semihost SYS_READC implementation (v6), Alex Bennée, 2019/12/17
- Re: [PATCH] Semihost SYS_READC implementation (v6), Paolo Bonzini, 2019/12/17
- [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP), Alex Bennée, 2019/12/17
- Re: [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP),
Paolo Bonzini <=
- Re: [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP), Alex Bennée, 2019/12/17
- Re: [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP), Paolo Bonzini, 2019/12/17
- Re: [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP), Alex Bennée, 2019/12/17
- Re: [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP), Paolo Bonzini, 2019/12/17
- Re: [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP), Paolo Bonzini, 2019/12/17
- Re: [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP), Alex Bennée, 2019/12/18
- Re: [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP), Paolo Bonzini, 2019/12/18