virt: acrn: Introduce an interface for Service VM to control vCPU

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.

Cc: Zhi Wang <zhi.a.wang@intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Yu Wang <yu1.wang@intel.com>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Zhi Wang <zhi.a.wang@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shuo Liu <shuo.a.liu@intel.com>
Link: https://lore.kernel.org/r/20210207031040.49576-18-shuo.a.liu@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 48 insertions, 0 deletions

diff --git a/drivers/virt/acrn/hsm.c b/drivers/virt/acrn/hsm.c
index 93f6abe10fa6..1f6b7c54a1a4 100644
--- a/drivers/virt/acrn/hsm.c
+++ b/drivers/virt/acrn/hsm.c
@@ -9,6 +9,7 @@
  *	Yakui Zhao <yakui.zhao@intel.com>
  */
 
+#include <linux/cpu.h>
 #include <linux/io.h>
 #include <linux/mm.h>
 #include <linux/module.h>
@@ -371,6 +372,52 @@ static int acrn_dev_release(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+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;
+	dev_dbg(dev, "Try to remove cpu %lld with lapicid %lld\n", cpu, lapicid);
+	ret = hcall_sos_remove_cpu(lapicid);
+	if (ret < 0) {
+		dev_err(dev, "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 const struct attribute_group *acrn_attr_groups[] = {
+	&acrn_attr_group,
+	NULL
+};
+
 static const struct file_operations acrn_fops = {
 	.owner		= THIS_MODULE,
 	.open		= acrn_dev_open,
@@ -382,6 +429,7 @@ struct miscdevice acrn_dev = {
 	.minor	= MISC_DYNAMIC_MINOR,
 	.name	= "acrn_hsm",
 	.fops	= &acrn_fops,
+	.groups	= acrn_attr_groups,
 };
 
 static int __init hsm_init(void)