mshv: Get the vmm capabilities offered by the hypervisor

Some hypervisor APIs are gated by feature bits in the
"vmm capabilities" partition property. Store the capabilities on
mshv_root module init, using HVCALL_GET_PARTITION_PROPERTY_EX.

This is not supported on all hypervisors. In that case, just set the
capabilities to 0 and proceed as normal.

Signed-off-by: Purna Pavan Chandra Aekkaladevi <paekkaladevi@linux.microsoft.com>
Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Praveen K Paladugu <prapal@linux.microsoft.com>
Reviewed-by: Easwar Hariharan <easwar.hariharan@linux.microsoft.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>

Author: pupacha

drivers/hv/mshv_root.h

@@ -178,6 +178,7 @@ struct mshv_root {
 	struct hv_synic_pages __percpu *synic_pages;
 	spinlock_t pt_ht_lock;
 	DECLARE_HASHTABLE(pt_htable, MSHV_PARTITIONS_HASH_BITS);
+	struct hv_partition_property_vmm_capabilities vmm_caps;
 };
 
 /*

drivers/hv/mshv_root_main.c

@@ -2203,6 +2203,22 @@ static int __init mshv_root_partition_init(struct device *dev)
 	return err;
 }
 
+static void mshv_init_vmm_caps(struct device *dev)
+{
+	/*
+	 * This can only fail here if HVCALL_GET_PARTITION_PROPERTY_EX or
+	 * HV_PARTITION_PROPERTY_VMM_CAPABILITIES are not supported. In that
+	 * case it's valid to proceed as if all vmm_caps are disabled (zero).
+	 */
+	if (hv_call_get_partition_property_ex(HV_PARTITION_ID_SELF,
+					      HV_PARTITION_PROPERTY_VMM_CAPABILITIES,
+					      0, &mshv_root.vmm_caps,
+					      sizeof(mshv_root.vmm_caps)))
+		dev_warn(dev, "Unable to get VMM capabilities\n");
+
+	dev_dbg(dev, "vmm_caps = %#llx\n", mshv_root.vmm_caps.as_uint64[0]);
+}
+
 static int __init mshv_parent_partition_init(void)
 {
 	int ret;
@@ -2255,6 +2271,8 @@ static int __init mshv_parent_partition_init(void)
 	if (ret)
 		goto remove_cpu_state;
 
+	mshv_init_vmm_caps(dev);
+
 	ret = mshv_irqfd_wq_init();
 	if (ret)
 		goto exit_partition;