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accel: introduce accelerator blocker API

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This API allows the accelerators to prevent vcpus from issuing
new ioctls while execting a critical section marked with the
accel_ioctl_inhibit_begin/end functions.

Note that all functions submitting ioctls must mark where the
ioctl is being called with accel_{cpu_}ioctl_begin/end().

This API requires the caller to always hold the BQL.
API documentation is in sysemu/accel-blocker.h

Internally, it uses a QemuLockCnt together with a per-CPU QemuLockCnt
(to minimize cache line bouncing) to keep avoid that new ioctls
run when the critical section starts, and a QemuEvent to wait
that all running ioctls finish.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20221111154758.1372674-2-eesposit@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Emanuele Giuseppe Esposito 2022-11-11 10:47:56 -05:00 • committed by Paolo Bonzini
parent b585edca34
commit bd688fc931
6 changed files with 217 additions and 2 deletions
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2
hw/core/cpu-common.c
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@ -238,6 +238,7 @@ static void cpu_common_initfn(Object *obj)
cpu->cflags_next_tb = -1;
qemu_mutex_init(&cpu->work_mutex);
qemu_lockcnt_init(&cpu->in_ioctl_lock);
QSIMPLEQ_INIT(&cpu->work_list);
QTAILQ_INIT(&cpu->breakpoints);
QTAILQ_INIT(&cpu->watchpoints);
@ -249,6 +250,7 @@ static void cpu_common_finalize(Object *obj)
{
CPUState *cpu = CPU(obj);
qemu_lockcnt_destroy(&cpu->in_ioctl_lock);
qemu_mutex_destroy(&cpu->work_mutex);
}