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/*
* Lock to inhibit accelerator ioctls
*
* Copyright (c) 2022 Red Hat Inc.
*
* Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
*
* 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 "qemu/thread.h"
#include "qemu/main-loop.h"
#include "hw/core/cpu.h"
#include "sysemu/accel-blocker.h"
static QemuLockCnt accel_in_ioctl_lock;
static QemuEvent accel_in_ioctl_event;
void accel_blocker_init(void)
{
qemu_lockcnt_init(&accel_in_ioctl_lock);
qemu_event_init(&accel_in_ioctl_event, false);
}
void accel_ioctl_begin(void)
{
if (likely(qemu_mutex_iothread_locked())) {
return;
}
/* block if lock is taken in kvm_ioctl_inhibit_begin() */
qemu_lockcnt_inc(&accel_in_ioctl_lock);
}
void accel_ioctl_end(void)
{
if (likely(qemu_mutex_iothread_locked())) {
return;
}
qemu_lockcnt_dec(&accel_in_ioctl_lock);
/* change event to SET. If event was BUSY, wake up all waiters */
qemu_event_set(&accel_in_ioctl_event);
}
void accel_cpu_ioctl_begin(CPUState *cpu)
{
if (unlikely(qemu_mutex_iothread_locked())) {
return;
}
/* block if lock is taken in kvm_ioctl_inhibit_begin() */
qemu_lockcnt_inc(&cpu->in_ioctl_lock);
}
void accel_cpu_ioctl_end(CPUState *cpu)
{
if (unlikely(qemu_mutex_iothread_locked())) {
return;
}
qemu_lockcnt_dec(&cpu->in_ioctl_lock);
/* change event to SET. If event was BUSY, wake up all waiters */
qemu_event_set(&accel_in_ioctl_event);
}
static bool accel_has_to_wait(void)
{
CPUState *cpu;
bool needs_to_wait = false;
CPU_FOREACH(cpu) {
if (qemu_lockcnt_count(&cpu->in_ioctl_lock)) {
/* exit the ioctl, if vcpu is running it */
qemu_cpu_kick(cpu);
needs_to_wait = true;
}
}
return needs_to_wait || qemu_lockcnt_count(&accel_in_ioctl_lock);
}
void accel_ioctl_inhibit_begin(void)
{
CPUState *cpu;
/*
* We allow to inhibit only when holding the BQL, so we can identify
* when an inhibitor wants to issue an ioctl easily.
*/
g_assert(qemu_mutex_iothread_locked());
/* Block further invocations of the ioctls outside the BQL. */
CPU_FOREACH(cpu) {
qemu_lockcnt_lock(&cpu->in_ioctl_lock);
}
qemu_lockcnt_lock(&accel_in_ioctl_lock);
/* Keep waiting until there are running ioctls */
while (true) {
/* Reset event to FREE. */
qemu_event_reset(&accel_in_ioctl_event);
if (accel_has_to_wait()) {
/*
* If event is still FREE, and there are ioctls still in progress,
* wait.
*
* If an ioctl finishes before qemu_event_wait(), it will change
* the event state to SET. This will prevent qemu_event_wait() from
* blocking, but it's not a problem because if other ioctls are
* still running the loop will iterate once more and reset the event
* status to FREE so that it can wait properly.
*
* If an ioctls finishes while qemu_event_wait() is blocking, then
* it will be waken up, but also here the while loop makes sure
* to re-enter the wait if there are other running ioctls.
*/
qemu_event_wait(&accel_in_ioctl_event);
} else {
/* No ioctl is running */
return;
}
}
}
void accel_ioctl_inhibit_end(void)
{
CPUState *cpu;
qemu_lockcnt_unlock(&accel_in_ioctl_lock);
CPU_FOREACH(cpu) {
qemu_lockcnt_unlock(&cpu->in_ioctl_lock);
}
}
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