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tcg: remove global exit_request

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There are now only two uses of the global exit_request left.

The first ensures we exit the run_loop when we first start to process
pending work and in the kick handler. This is just as easily done by
setting the first_cpu->exit_request flag.

The second use is in the round robin kick routine. The global
exit_request ensured every vCPU would set its local exit_request and
cause a full exit of the loop. Now the iothread isn't being held while
running we can just rely on the kick handler to push us out as intended.

We lightly re-factor the main vCPU thread to ensure cpu->exit_requests
cause us to exit the main loop and process any IO requests that might
come along. As an cpu->exit_request may legitimately get squashed
while processing the EXCP_INTERRUPT exception we also check
cpu->queued_work_first to ensure queued work is expedited as soon as
possible.

Backports commit e5143e30fb87fbf179029387f83f98a5a9b27f19 from qemu
This commit is contained in:
Alex Bennée 2018-03-02 09:36:41 -05:00 committed by Lioncash
parent 4d90497d14
commit 632b853761
No known key found for this signature in database
GPG key ID: 4E3C3CC1031BA9C7
3 changed files with 13 additions and 21 deletions
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1
include/uc_priv.h
View file

@ -193,7 +193,6 @@ struct uc_struct {
// qemu/cpu-exec.c
BounceBuffer bounce;
volatile sig_atomic_t exit_request;
CPUState *tcg_current_rr_cpu;
// qemu/memory.c

20
qemu/cpu-exec.c
View file

@ -400,15 +400,13 @@ static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb,
*tb_exit = ret & TB_EXIT_MASK;
switch (*tb_exit) {
case TB_EXIT_REQUESTED:
/* Something asked us to stop executing
* chained TBs; just continue round the main
* loop. Whatever requested the exit will also
* have set something else (eg exit_request or
* interrupt_request) which we will handle
* next time around the loop. But we need to
* ensure the zeroing of tcg_exit_req (see cpu_tb_exec)
* comes before the next read of cpu->exit_request
* or cpu->interrupt_request.
/* Something asked us to stop executing chained TBs; just
* continue round the main loop. Whatever requested the exit
* will also have set something else (eg interrupt_request)
* which we will handle next time around the loop. But we
* need to ensure the tcg_exit_req read in generated code
* comes before the next read of cpu->exit_request or
* cpu->interrupt_request.
*/
smp_mb();
*last_tb = NULL;
@ -494,10 +492,6 @@ int cpu_exec(struct uc_struct *uc, CPUState *cpu)
atomic_mb_set(&uc->current_cpu, cpu);
atomic_mb_set(&uc->tcg_current_rr_cpu, cpu);
if (unlikely(atomic_mb_read(&uc->exit_request))) {
cpu->exit_request = 1;
}
cc->cpu_exec_enter(cpu);
cpu->exception_index = -1;
env->invalid_error = UC_ERR_OK;

11
qemu/cpus.c
View file

@ -150,7 +150,7 @@ static bool tcg_exec_all(struct uc_struct* uc)
{
int r;
bool finish = false;
while (!uc->exit_request) {
while (!uc->cpu->exit_request) {
CPUState *cpu = uc->cpu;
CPUArchState *env = cpu->env_ptr;
@ -165,27 +165,23 @@ static bool tcg_exec_all(struct uc_struct* uc)
// reset stop_request
uc->stop_request = false;
} else if (uc->stop_request) {
//printf(">>> got STOP request!!!\n");
finish = true;
break;
}
// save invalid memory access error & quit
if (env->invalid_error) {
// printf(">>> invalid memory accessed, STOP = %u!!!\n", env->invalid_error);
uc->invalid_addr = env->invalid_addr;
uc->invalid_error = env->invalid_error;
finish = true;
break;
}
// printf(">>> stop with r = %x, HLT=%x\n", r, EXCP_HLT);
if (r == EXCP_DEBUG) {
cpu_handle_guest_debug(cpu);
break;
}
if (r == EXCP_HLT) {
//printf(">>> got HLT!!!\n");
finish = true;
break;
} else if (r == EXCP_ATOMIC) {
@ -196,7 +192,10 @@ static bool tcg_exec_all(struct uc_struct* uc)
break;
}
}
uc->exit_request = 0;
if (uc->cpu && uc->cpu->exit_request) {
atomic_mb_set(&uc->cpu->exit_request, 0);
}
return finish;
}