[PATCH 17/17] virt: acrn: Introduce an interface for Service VM to control vCPU

[shuo . a . liu]

From: Shuo Liu <shuo.a.liu@xxxxxxxxx>

ACRN supports partition mode to achieve real-time requirements. In
partition mode, a CPU core can be dedicated to a vCPU of User VM. The
local APIC of the dedicated CPU core can be passthrough to the User VM.
The Service VM controls the assignment of the CPU cores.

Introduce an interface for the Service VM to remove the control of CPU
core from hypervisor perspective so that the CPU core can be a dedicated
CPU core of User VM.

Signed-off-by: Shuo Liu <shuo.a.liu@xxxxxxxxx>
Reviewed-by: Zhi Wang <zhi.a.wang@xxxxxxxxx>
Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Cc: Zhi Wang <zhi.a.wang@xxxxxxxxx>
Cc: Zhenyu Wang <zhenyuw@xxxxxxxxxxxxxxx>
Cc: Yu Wang <yu1.wang@xxxxxxxxx>
Cc: Reinette Chatre <reinette.chatre@xxxxxxxxx>
---
 drivers/virt/acrn/hsm.c       | 49 +++++++++++++++++++++++++++++++++++
 drivers/virt/acrn/hypercall.h | 12 +++++++++
 2 files changed, 61 insertions(+)

diff --git a/drivers/virt/acrn/hsm.c b/drivers/virt/acrn/hsm.c
index 81300ea19dc9..b1e87684701c 100644
--- a/drivers/virt/acrn/hsm.c
+++ b/drivers/virt/acrn/hsm.c
@@ -11,6 +11,7 @@
 
 #define pr_fmt(fmt) "acrn: " fmt
 
+#include <linux/cpu.h>
 #include <linux/io.h>
 #include <linux/miscdevice.h>
 #include <linux/mm.h>
@@ -348,6 +349,47 @@ static struct miscdevice acrn_dev = {
 	.fops	= &acrn_fops,
 };
 
+static ssize_t remove_cpu_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	u64 cpu, lapicid;
+	int ret;
+
+	if (kstrtoull(buf, 0, &cpu) < 0)
+		return -EINVAL;
+
+	if (cpu >= num_possible_cpus() || cpu == 0 || !cpu_is_hotpluggable(cpu))
+		return -EINVAL;
+
+	if (cpu_online(cpu))
+		remove_cpu(cpu);
+
+	lapicid = cpu_data(cpu).apicid;
+	pr_debug("Try to remove cpu %lld with lapicid %lld\n", cpu, lapicid);
+	ret = hcall_sos_remove_cpu(lapicid);
+	if (ret < 0) {
+		pr_err("Failed to remove cpu %lld!\n", cpu);
+		goto fail_remove;
+	}
+
+	return count;
+
+fail_remove:
+	add_cpu(cpu);
+	return ret;
+}
+static DEVICE_ATTR_WO(remove_cpu);
+
+static struct attribute *acrn_attrs[] = {
+	&dev_attr_remove_cpu.attr,
+	NULL
+};
+
+static struct attribute_group acrn_attr_group = {
+	.attrs = acrn_attrs,
+};
+
 static int __init hsm_init(void)
 {
 	int ret;
@@ -373,13 +415,20 @@ static int __init hsm_init(void)
 		return ret;
 	}
 
+	if (sysfs_create_group(&acrn_dev.this_device->kobj, &acrn_attr_group)) {
+		pr_warn("sysfs create failed\n");
+		misc_deregister(&acrn_dev);
+		return -EINVAL;
+	}
 	acrn_ioreq_intr_setup();
+
 	return 0;
 }
 
 static void __exit hsm_exit(void)
 {
 	acrn_ioreq_intr_remove();
+	sysfs_remove_group(&acrn_dev.this_device->kobj, &acrn_attr_group);
 	misc_deregister(&acrn_dev);
 }
 module_init(hsm_init);
diff --git a/drivers/virt/acrn/hypercall.h b/drivers/virt/acrn/hypercall.h
index ce8fdca76394..04121223ff8d 100644
--- a/drivers/virt/acrn/hypercall.h
+++ b/drivers/virt/acrn/hypercall.h
@@ -15,6 +15,7 @@
 
 #define HC_ID_GEN_BASE			0x0UL
 #define HC_GET_API_VERSION		_HC_ID(HC_ID, HC_ID_GEN_BASE + 0x00)
+#define HC_SOS_REMOVE_CPU		_HC_ID(HC_ID, HC_ID_GEN_BASE + 0x01)
 
 #define HC_ID_VM_BASE			0x10UL
 #define HC_CREATE_VM			_HC_ID(HC_ID, HC_ID_VM_BASE + 0x00)
@@ -56,6 +57,17 @@ static inline long hcall_get_api_version(u64 api_version)
 	return acrn_hypercall1(HC_GET_API_VERSION, api_version);
 }
 
+/**
+ * hcall_sos_remove_cpu() - Remove a vCPU of Service VM
+ * @cpu: The vCPU to be removed
+ *
+ * Return: 0 on success, <0 on failure
+ */
+static inline long hcall_sos_remove_cpu(u64 cpu)
+{
+	return acrn_hypercall1(HC_SOS_REMOVE_CPU, cpu);
+}
+
 /**
  * hcall_create_vm() - Create a User VM
  * @vminfo:	Service VM GPA of info of User VM creation
-- 
2.28.0