qemu-cr16/accel/tcg/tcg-accel-ops.c
Paolo Bonzini 9a191d3782 cpus: clear exit_request in qemu_process_cpu_events
Make the code common to all accelerators: after seeing cpu->exit_request
set to true, accelerator code needs to reach qemu_process_cpu_events_common().

So for the common cases where they use qemu_process_cpu_events(), go ahead and
clear it in there.  Note that the cheap qatomic_set() is enough because
at this point the thread has taken the BQL; qatomic_set_mb() is not needed.
In particular, this is the ordering of the communication between
I/O and vCPU threads is always the same.

In the I/O thread:

(a) store other memory locations that will be checked if cpu->exit_request
    or cpu->interrupt_request is 1 (for example cpu->stop or cpu->work_list
    for cpu->exit_request)

(b) cpu_exit(): store-release cpu->exit_request, or
(b) cpu_interrupt(): store-release cpu->interrupt_request

>>> at this point, cpu->halt_cond is broadcast and the BQL released

(c) do the accelerator-specific kick (e.g. write icount_decr for TCG,
    pthread_kill for KVM, etc.)

In the vCPU thread instead the opposite order is respected:

(c) the accelerator's execution loop exits thanks to the kick

(b) then the inner execution loop checks cpu->interrupt_request
    and cpu->exit_request.  If needed cpu->interrupt_request is
    converted into cpu->exit_request when work is needed outside
    the execution loop.

(a) then the other memory locations are checked.  Some may need to
    be read under the BQL, but the vCPU thread may also take other
    locks (e.g. for queued work items) or none at all.

qatomic_set_mb() would only be needed if the halt sleep was done
outside the BQL (though in that case, cpu->exit_request probably
would be replaced by a QemuEvent or something like that).

Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2025-09-17 19:00:56 +02:00

249 lines
6.8 KiB
C

/*
* QEMU TCG vCPU common functionality
*
* Functionality common to all TCG vCPU variants: mttcg, rr and icount.
*
* Copyright (c) 2003-2008 Fabrice Bellard
* Copyright (c) 2014 Red Hat Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu/osdep.h"
#include "accel/accel-ops.h"
#include "accel/accel-cpu-ops.h"
#include "system/tcg.h"
#include "system/replay.h"
#include "exec/icount.h"
#include "qemu/main-loop.h"
#include "qemu/guest-random.h"
#include "qemu/timer.h"
#include "exec/cputlb.h"
#include "exec/hwaddr.h"
#include "exec/tb-flush.h"
#include "exec/translation-block.h"
#include "exec/watchpoint.h"
#include "gdbstub/enums.h"
#include "hw/core/cpu.h"
#include "tcg-accel-ops.h"
#include "tcg-accel-ops-mttcg.h"
#include "tcg-accel-ops-rr.h"
#include "tcg-accel-ops-icount.h"
/* common functionality among all TCG variants */
void tcg_cpu_init_cflags(CPUState *cpu, bool parallel)
{
uint32_t cflags;
/*
* Include the cluster number in the hash we use to look up TBs.
* This is important because a TB that is valid for one cluster at
* a given physical address and set of CPU flags is not necessarily
* valid for another:
* the two clusters may have different views of physical memory, or
* may have different CPU features (eg FPU present or absent).
*/
cflags = cpu->cluster_index << CF_CLUSTER_SHIFT;
cflags |= parallel ? CF_PARALLEL : 0;
cflags |= icount_enabled() ? CF_USE_ICOUNT : 0;
tcg_cflags_set(cpu, cflags);
}
void tcg_cpu_destroy(CPUState *cpu)
{
cpu_thread_signal_destroyed(cpu);
}
int tcg_cpu_exec(CPUState *cpu)
{
int ret;
assert(tcg_enabled());
cpu_exec_start(cpu);
ret = cpu_exec(cpu);
cpu_exec_end(cpu);
return ret;
}
static void tcg_cpu_reset_hold(CPUState *cpu)
{
tcg_flush_jmp_cache(cpu);
tlb_flush(cpu);
}
/* mask must never be zero, except for A20 change call */
void tcg_handle_interrupt(CPUState *cpu, int mask)
{
cpu_set_interrupt(cpu, mask);
/*
* If called from iothread context, wake the target cpu in
* case its halted.
*/
if (!qemu_cpu_is_self(cpu)) {
qemu_cpu_kick(cpu);
} else {
qatomic_set(&cpu->neg.icount_decr.u16.high, -1);
}
}
static bool tcg_supports_guest_debug(void)
{
return true;
}
/* Translate GDB watchpoint type to a flags value for cpu_watchpoint_* */
static inline int xlat_gdb_type(CPUState *cpu, int gdbtype)
{
static const int xlat[] = {
[GDB_WATCHPOINT_WRITE] = BP_GDB | BP_MEM_WRITE,
[GDB_WATCHPOINT_READ] = BP_GDB | BP_MEM_READ,
[GDB_WATCHPOINT_ACCESS] = BP_GDB | BP_MEM_ACCESS,
};
int cputype = xlat[gdbtype];
if (cpu->cc->gdb_stop_before_watchpoint) {
cputype |= BP_STOP_BEFORE_ACCESS;
}
return cputype;
}
static int tcg_insert_breakpoint(CPUState *cs, int type, vaddr addr, vaddr len)
{
CPUState *cpu;
int err = 0;
switch (type) {
case GDB_BREAKPOINT_SW:
case GDB_BREAKPOINT_HW:
CPU_FOREACH(cpu) {
err = cpu_breakpoint_insert(cpu, addr, BP_GDB, NULL);
if (err) {
break;
}
}
return err;
case GDB_WATCHPOINT_WRITE:
case GDB_WATCHPOINT_READ:
case GDB_WATCHPOINT_ACCESS:
CPU_FOREACH(cpu) {
err = cpu_watchpoint_insert(cpu, addr, len,
xlat_gdb_type(cpu, type), NULL);
if (err) {
break;
}
}
return err;
default:
return -ENOSYS;
}
}
static int tcg_remove_breakpoint(CPUState *cs, int type, vaddr addr, vaddr len)
{
CPUState *cpu;
int err = 0;
switch (type) {
case GDB_BREAKPOINT_SW:
case GDB_BREAKPOINT_HW:
CPU_FOREACH(cpu) {
err = cpu_breakpoint_remove(cpu, addr, BP_GDB);
if (err) {
break;
}
}
return err;
case GDB_WATCHPOINT_WRITE:
case GDB_WATCHPOINT_READ:
case GDB_WATCHPOINT_ACCESS:
CPU_FOREACH(cpu) {
err = cpu_watchpoint_remove(cpu, addr, len,
xlat_gdb_type(cpu, type));
if (err) {
break;
}
}
return err;
default:
return -ENOSYS;
}
}
static inline void tcg_remove_all_breakpoints(CPUState *cpu)
{
cpu_breakpoint_remove_all(cpu, BP_GDB);
cpu_watchpoint_remove_all(cpu, BP_GDB);
}
static void tcg_accel_ops_init(AccelClass *ac)
{
AccelOpsClass *ops = ac->ops;
if (qemu_tcg_mttcg_enabled()) {
ops->create_vcpu_thread = mttcg_start_vcpu_thread;
ops->kick_vcpu_thread = tcg_kick_vcpu_thread;
ops->handle_interrupt = tcg_handle_interrupt;
} else {
ops->create_vcpu_thread = rr_start_vcpu_thread;
ops->kick_vcpu_thread = rr_kick_vcpu_thread;
if (icount_enabled()) {
ops->handle_interrupt = icount_handle_interrupt;
ops->get_virtual_clock = icount_get;
ops->get_elapsed_ticks = icount_get;
} else {
ops->handle_interrupt = tcg_handle_interrupt;
}
}
ops->cpu_reset_hold = tcg_cpu_reset_hold;
ops->supports_guest_debug = tcg_supports_guest_debug;
ops->insert_breakpoint = tcg_insert_breakpoint;
ops->remove_breakpoint = tcg_remove_breakpoint;
ops->remove_all_breakpoints = tcg_remove_all_breakpoints;
}
static void tcg_accel_ops_class_init(ObjectClass *oc, const void *data)
{
AccelOpsClass *ops = ACCEL_OPS_CLASS(oc);
ops->ops_init = tcg_accel_ops_init;
}
static const TypeInfo tcg_accel_ops_type = {
.name = ACCEL_OPS_NAME("tcg"),
.parent = TYPE_ACCEL_OPS,
.class_init = tcg_accel_ops_class_init,
.abstract = true,
};
module_obj(ACCEL_OPS_NAME("tcg"));
static void tcg_accel_ops_register_types(void)
{
type_register_static(&tcg_accel_ops_type);
}
type_init(tcg_accel_ops_register_types);