bd688fc931
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>
57 lines
1.7 KiB
C
57 lines
1.7 KiB
C
/*
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* Accelerator blocking API, to prevent new ioctls from starting and wait the
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* running ones finish.
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* This mechanism differs from pause/resume_all_vcpus() in that it does not
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* release the BQL.
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*
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* Copyright (c) 2022 Red Hat Inc.
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*
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* Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#ifndef ACCEL_BLOCKER_H
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#define ACCEL_BLOCKER_H
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#include "qemu/osdep.h"
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#include "sysemu/cpus.h"
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extern void accel_blocker_init(void);
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/*
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* accel_{cpu_}ioctl_begin/end:
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* Mark when ioctl is about to run or just finished.
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*
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* accel_{cpu_}ioctl_begin will block after accel_ioctl_inhibit_begin() is
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* called, preventing new ioctls to run. They will continue only after
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* accel_ioctl_inibith_end().
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*/
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extern void accel_ioctl_begin(void);
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extern void accel_ioctl_end(void);
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extern void accel_cpu_ioctl_begin(CPUState *cpu);
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extern void accel_cpu_ioctl_end(CPUState *cpu);
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/*
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* accel_ioctl_inhibit_begin: start critical section
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*
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* This function makes sure that:
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* 1) incoming accel_{cpu_}ioctl_begin() calls block
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* 2) wait that all ioctls that were already running reach
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* accel_{cpu_}ioctl_end(), kicking vcpus if necessary.
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*
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* This allows the caller to access shared data or perform operations without
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* worrying of concurrent vcpus accesses.
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*/
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extern void accel_ioctl_inhibit_begin(void);
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/*
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* accel_ioctl_inhibit_end: end critical section started by
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* accel_ioctl_inhibit_begin()
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*
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* This function allows blocked accel_{cpu_}ioctl_begin() to continue.
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*/
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extern void accel_ioctl_inhibit_end(void);
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#endif /* ACCEL_BLOCKER_H */
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