[PATCH RFC v15 24/30] virt: gunyah: Share guest VM dtb configuration to Gunyah

[Elliot Berman]

Gunyah Resource Manager sets up a virtual machine based on a device tree
which lives in guest memory. Resource manager requires this memory to be
provided as a memory parcel for it to read and manipulate. Construct a
memory parcel, lend it to the virtual machine, and inform resource
manager about the device tree location (the memory parcel ID and offset
into the memory parcel).

Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
---
 drivers/virt/gunyah/vm_mgr.c | 46 ++++++++++++++++++++++++++++++++++++++++++--
 drivers/virt/gunyah/vm_mgr.h |  6 ++++++
 include/uapi/linux/gunyah.h  | 14 ++++++++++++++
 3 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/drivers/virt/gunyah/vm_mgr.c b/drivers/virt/gunyah/vm_mgr.c
index a31a9f0a642c..8f8d962c9f8c 100644
--- a/drivers/virt/gunyah/vm_mgr.c
+++ b/drivers/virt/gunyah/vm_mgr.c
@@ -627,8 +627,27 @@ static int gunyah_vm_start(struct gunyah_vm *ghvm)
 	ghvm->vmid = ret;
 	ghvm->vm_status = GUNYAH_RM_VM_STATUS_LOAD;
 
-	ret = gunyah_rm_vm_configure(ghvm->rm, ghvm->vmid, ghvm->auth, 0, 0, 0,
-				     0, 0);
+	ghvm->dtb.parcel_start = ghvm->dtb.config.guest_phys_addr >> PAGE_SHIFT;
+	ghvm->dtb.parcel_pages = ghvm->dtb.config.size >> PAGE_SHIFT;
+	/* RM requires the DTB parcel to be lent to guard against malicious
+	 * modifications while starting VM. Force it so.
+	 */
+	ghvm->dtb.parcel.n_acl_entries = 1;
+	ret = gunyah_gmem_share_parcel(ghvm, &ghvm->dtb.parcel,
+				       &ghvm->dtb.parcel_start,
+				       &ghvm->dtb.parcel_pages);
+	if (ret) {
+		dev_warn(ghvm->parent,
+			 "Failed to allocate parcel for DTB: %d\n", ret);
+		goto err;
+	}
+
+	ret = gunyah_rm_vm_configure(ghvm->rm, ghvm->vmid, ghvm->auth,
+				     ghvm->dtb.parcel.mem_handle, 0, 0,
+				     ghvm->dtb.config.guest_phys_addr -
+					     (ghvm->dtb.parcel_start
+					      << PAGE_SHIFT),
+				     ghvm->dtb.config.size);
 	if (ret) {
 		dev_warn(ghvm->parent, "Failed to configure VM: %d\n", ret);
 		goto err;
@@ -720,6 +739,21 @@ static long gunyah_vm_ioctl(struct file *filp, unsigned int cmd,
 	long r;
 
 	switch (cmd) {
+	case GUNYAH_VM_SET_DTB_CONFIG: {
+		struct gunyah_vm_dtb_config dtb_config;
+
+		if (copy_from_user(&dtb_config, argp, sizeof(dtb_config)))
+			return -EFAULT;
+
+		if (overflows_type(dtb_config.guest_phys_addr + dtb_config.size,
+				   u64))
+			return -EOVERFLOW;
+
+		ghvm->dtb.config = dtb_config;
+
+		r = 0;
+		break;
+	}
 	case GUNYAH_VM_START: {
 		r = gunyah_vm_ensure_started(ghvm);
 		break;
@@ -783,6 +817,14 @@ static void _gunyah_vm_put(struct kref *kref)
 		gunyah_vm_stop(ghvm);
 
 	gunyah_vm_remove_functions(ghvm);
+	if (ghvm->vm_status == GUNYAH_RM_VM_STATUS_LOAD) {
+		ret = gunyah_gmem_reclaim_parcel(ghvm, &ghvm->dtb.parcel,
+						 ghvm->dtb.parcel_start,
+						 ghvm->dtb.parcel_pages);
+		if (ret)
+			dev_err(ghvm->parent,
+				"Failed to reclaim DTB parcel: %d\n", ret);
+	}
 
 	mt_for_each(&ghvm->mem_layout, b, idx, ULONG_MAX)
 		gunyah_gmem_remove_binding(b);
diff --git a/drivers/virt/gunyah/vm_mgr.h b/drivers/virt/gunyah/vm_mgr.h
index a7fc7c376d1e..357414e67d72 100644
--- a/drivers/virt/gunyah/vm_mgr.h
+++ b/drivers/virt/gunyah/vm_mgr.h
@@ -60,6 +60,12 @@ struct gunyah_vm {
 	struct list_head resource_tickets;
 	struct rb_root mmio_handler_root;
 	struct rw_semaphore mmio_handler_lock;
+
+	struct {
+		struct gunyah_vm_dtb_config config;
+		u64 parcel_start, parcel_pages;
+		struct gunyah_rm_mem_parcel parcel;
+	} dtb;
 	struct xarray boot_context;
 };
 
diff --git a/include/uapi/linux/gunyah.h b/include/uapi/linux/gunyah.h
index a171185191ae..574116f54472 100644
--- a/include/uapi/linux/gunyah.h
+++ b/include/uapi/linux/gunyah.h
@@ -42,6 +42,20 @@ struct gunyah_create_mem_args {
 /*
  * ioctls for gunyah-vm fds (returned by GUNYAH_CREATE_VM)
  */
+
+/**
+ * struct gunyah_vm_dtb_config - Set the location of the VM's devicetree blob
+ * @guest_phys_addr: Address of the VM's devicetree in guest memory.
+ * @size: Maximum size of the devicetree including space for overlays.
+ *        Resource manager applies an overlay to the DTB and dtb_size should
+ *        include room for the overlay. A page of memory is typicaly plenty.
+ */
+struct gunyah_vm_dtb_config {
+	__u64 guest_phys_addr;
+	__u64 size;
+};
+#define GUNYAH_VM_SET_DTB_CONFIG	_IOW(GUNYAH_IOCTL_TYPE, 0x2, struct gunyah_vm_dtb_config)
+
 #define GUNYAH_VM_START		_IO(GUNYAH_IOCTL_TYPE, 0x3)
 
 /**

-- 
2.43.0