Commit b3562c60 authored Jun 11, 2020 by David Hildenbrand Committed by Michael S. Tsirkin Jun 22, 2020

virtio-mem: add memory via add_memory_driver_managed()



Virtio-mem managed memory is always detected and added by the virtio-mem
driver, never using something like the firmware-provided memory map.
This is the case after an ordinary system reboot, and has to be guaranteed
after kexec. Especially, virtio-mem added memory resources can contain
inaccessible parts ("unblocked memory blocks"), blindly forwarding them
to a kexec kernel is dangerous, as unplugged memory will get accessed
(esp. written).

Let's use the new way of adding special driver-managed memory introduced
in commit 7b7b2721 ("mm/memory_hotplug: introduce
add_memory_driver_managed()").

This will result in no entries in /sys/firmware/memmap ("raw firmware-
provided memory map"), the memory resource will be flagged
IORESOURCE_MEM_DRIVER_MANAGED (esp., kexec_file_load() will not place
kexec images on this memory), and it is exposed as "System RAM
(virtio_mem)" in /proc/iomem, so esp. kexec-tools can properly handle it.

Example /proc/iomem before this change:
  [...]
  140000000-333ffffff : virtio0
    140000000-147ffffff : System RAM
  334000000-533ffffff : virtio1
    338000000-33fffffff : System RAM
    340000000-347ffffff : System RAM
    348000000-34fffffff : System RAM
  [...]

Example /proc/iomem after this change:
  [...]
  140000000-333ffffff : virtio0
    140000000-147ffffff : System RAM (virtio_mem)
  334000000-533ffffff : virtio1
    338000000-33fffffff : System RAM (virtio_mem)
    340000000-347ffffff : System RAM (virtio_mem)
    348000000-34fffffff : System RAM (virtio_mem)
  [...]

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Fixes: 5f1f79bb ("virtio-mem: Paravirtualized memory hotplug")
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20200611093518.5737-1-david@redhat.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>

parent 1c3d69ab

drivers/virtio/virtio_mem.c

+22 −3

Original line number	Diff line number	Diff line
		@@ -101,6 +101,11 @@ struct virtio_mem {

		/* The parent resource for all memory added via this device. */
		struct resource *parent_resource;
		/*
		* Copy of "System RAM (virtio_mem)" to be used for
		* add_memory_driver_managed().
		*/
		const char *resource_name;

		/* Summary of all memory block states. */
		unsigned long nb_mb_state[VIRTIO_MEM_MB_STATE_COUNT];
		@@ -414,8 +419,20 @@ static int virtio_mem_mb_add(struct virtio_mem *vm, unsigned long mb_id)
		if (nid == NUMA_NO_NODE)
		nid = memory_add_physaddr_to_nid(addr);

		/*
		* When force-unloading the driver and we still have memory added to
		* Linux, the resource name has to stay.
		*/
		if (!vm->resource_name) {
		vm->resource_name = kstrdup_const("System RAM (virtio_mem)",
		GFP_KERNEL);
		if (!vm->resource_name)
		return -ENOMEM;
		}

		dev_dbg(&vm->vdev->dev, "adding memory block: %lu\n", mb_id);
		return add_memory(nid, addr, memory_block_size_bytes());
		return add_memory_driver_managed(nid, addr, memory_block_size_bytes(),
		vm->resource_name);
		}

		/*
		@@ -1890,10 +1907,12 @@ static void virtio_mem_remove(struct virtio_device *vdev)
		vm->nb_mb_state[VIRTIO_MEM_MB_STATE_OFFLINE_PARTIAL] \|\|
		vm->nb_mb_state[VIRTIO_MEM_MB_STATE_ONLINE] \|\|
		vm->nb_mb_state[VIRTIO_MEM_MB_STATE_ONLINE_PARTIAL] \|\|
		vm->nb_mb_state[VIRTIO_MEM_MB_STATE_ONLINE_MOVABLE])
		vm->nb_mb_state[VIRTIO_MEM_MB_STATE_ONLINE_MOVABLE]) {
		dev_warn(&vdev->dev, "device still has system memory added\n");
		else
		} else {
		virtio_mem_delete_resource(vm);
		kfree_const(vm->resource_name);
		}

		/* remove all tracking data - no locking needed */
		vfree(vm->mb_state);

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