[RFC PATCH 5/7] accel/hw: Implement hw_accel_get_cpus_queue()

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

We can only run a single hardware accelerator at a time,
so add a generic hw_accel_get_cpus_queue() helper in
accel-system.c, a file common to all HW accelerators.

Register AccelOpsClass::get_cpus_queue() for each HW
accelerator. Add a generic CPU_FOREACH_HWACCEL() macro.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/system/hw_accel.h         | 9 +++++++++
 accel/accel-system.c              | 8 ++++++++
 accel/kvm/kvm-accel-ops.c         | 1 +
 accel/xen/xen-all.c               | 1 +
 target/i386/nvmm/nvmm-accel-ops.c | 1 +
 target/i386/whpx/whpx-accel-ops.c | 1 +
 6 files changed, 21 insertions(+)

diff --git a/include/system/hw_accel.h b/include/system/hw_accel.h
index 380e9e640b6..12664cac6f9 100644
--- a/include/system/hw_accel.h
+++ b/include/system/hw_accel.h
@@ -2,6 +2,7 @@
  * QEMU Hardware accelerators support
  *
  * Copyright 2016 Google, Inc.
+ * Copyright 2025 Linaro Ltd.
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  * See the COPYING file in the top-level directory.
@@ -17,6 +18,14 @@
 #include "system/whpx.h"
 #include "system/nvmm.h"
 
+/* Guard with qemu_cpu_list_lock */
+extern CPUTailQ hw_accel_cpus_queue;
+
+#define CPU_FOREACH_HWACCEL(cpu) \
+            QTAILQ_FOREACH_RCU(cpu, &hw_accel_cpus_queue, node)
+
+CPUTailQ *hw_accel_get_cpus_queue(void);
+
 void cpu_synchronize_state(CPUState *cpu);
 void cpu_synchronize_post_reset(CPUState *cpu);
 void cpu_synchronize_post_init(CPUState *cpu);
diff --git a/accel/accel-system.c b/accel/accel-system.c
index a7596aef59d..60877ea7a28 100644
--- a/accel/accel-system.c
+++ b/accel/accel-system.c
@@ -27,9 +27,17 @@
 #include "qemu/accel.h"
 #include "hw/boards.h"
 #include "system/cpus.h"
+#include "system/hw_accel.h"
 #include "qemu/error-report.h"
 #include "accel-system.h"
 
+CPUTailQ hw_accel_cpus_queue = QTAILQ_HEAD_INITIALIZER(hw_accel_cpus_queue);
+
+CPUTailQ *hw_accel_get_cpus_queue(void)
+{
+    return &hw_accel_cpus_queue;
+}
+
 int accel_init_machine(AccelState *accel, MachineState *ms)
 {
     AccelClass *acc = ACCEL_GET_CLASS(accel);
diff --git a/accel/kvm/kvm-accel-ops.c b/accel/kvm/kvm-accel-ops.c
index a81e8f3b03b..5f4001860d5 100644
--- a/accel/kvm/kvm-accel-ops.c
+++ b/accel/kvm/kvm-accel-ops.c
@@ -93,6 +93,7 @@ static void kvm_accel_ops_class_init(ObjectClass *oc, void *data)
 {
     AccelOpsClass *ops = ACCEL_OPS_CLASS(oc);
 
+    ops->get_cpus_queue = hw_accel_get_cpus_queue;
     ops->create_vcpu_thread = kvm_start_vcpu_thread;
     ops->cpu_thread_is_idle = kvm_vcpu_thread_is_idle;
     ops->cpus_are_resettable = kvm_cpus_are_resettable;
diff --git a/accel/xen/xen-all.c b/accel/xen/xen-all.c
index 852e9fbe5fe..ac5ed2dfb80 100644
--- a/accel/xen/xen-all.c
+++ b/accel/xen/xen-all.c
@@ -150,6 +150,7 @@ static void xen_accel_ops_class_init(ObjectClass *oc, void *data)
 {
     AccelOpsClass *ops = ACCEL_OPS_CLASS(oc);
 
+    ops->get_cpus_queue = hw_accel_get_cpus_queue;
     ops->create_vcpu_thread = dummy_start_vcpu_thread;
 }
 
diff --git a/target/i386/nvmm/nvmm-accel-ops.c b/target/i386/nvmm/nvmm-accel-ops.c
index e7b56662fee..bb407c68e14 100644
--- a/target/i386/nvmm/nvmm-accel-ops.c
+++ b/target/i386/nvmm/nvmm-accel-ops.c
@@ -84,6 +84,7 @@ static void nvmm_accel_ops_class_init(ObjectClass *oc, void *data)
 {
     AccelOpsClass *ops = ACCEL_OPS_CLASS(oc);
 
+    ops->get_cpus_queue = hw_accel_get_cpus_queue;
     ops->create_vcpu_thread = nvmm_start_vcpu_thread;
     ops->kick_vcpu_thread = nvmm_kick_vcpu_thread;
 
diff --git a/target/i386/whpx/whpx-accel-ops.c b/target/i386/whpx/whpx-accel-ops.c
index ab2e014c9ea..191214ca81d 100644
--- a/target/i386/whpx/whpx-accel-ops.c
+++ b/target/i386/whpx/whpx-accel-ops.c
@@ -86,6 +86,7 @@ static void whpx_accel_ops_class_init(ObjectClass *oc, void *data)
 {
     AccelOpsClass *ops = ACCEL_OPS_CLASS(oc);
 
+    ops->get_cpus_queue = hw_accel_get_cpus_queue;
     ops->create_vcpu_thread = whpx_start_vcpu_thread;
     ops->kick_vcpu_thread = whpx_kick_vcpu_thread;
     ops->cpu_thread_is_idle = whpx_vcpu_thread_is_idle;
-- 
2.47.1