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    SubjectRe: [PATCH v4 11/15] virtio-mem: Add parent resource for all added "System RAM"
    > Let's add a parent resource, named after the virtio device (inspired by
    > drivers/dax/kmem.c). This allows user space to identify which memory
    > belongs to which virtio-mem device.
    >
    > With this change and two virtio-mem devices:
    > :/# cat /proc/iomem
    > 00000000-00000fff : Reserved
    > 00001000-0009fbff : System RAM
    > [...]
    > 140000000-333ffffff : virtio0
    > 140000000-147ffffff : System RAM
    > 148000000-14fffffff : System RAM
    > 150000000-157ffffff : System RAM
    > [...]
    > 334000000-3033ffffff : virtio1
    > 338000000-33fffffff : System RAM
    > 340000000-347ffffff : System RAM
    > 348000000-34fffffff : System RAM
    > [...]
    >
    > Cc: "Michael S. Tsirkin" <mst@redhat.com>
    > Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
    > Signed-off-by: David Hildenbrand <david@redhat.com>
    > ---
    > drivers/virtio/virtio_mem.c | 52 ++++++++++++++++++++++++++++++++++++-
    > 1 file changed, 51 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
    > index eb4c16d634e0..80cdb9e6b3c4 100644
    > --- a/drivers/virtio/virtio_mem.c
    > +++ b/drivers/virtio/virtio_mem.c
    > @@ -99,6 +99,9 @@ struct virtio_mem {
    > /* Id of the next memory bock to prepare when needed. */
    > unsigned long next_mb_id;
    >
    > + /* The parent resource for all memory added via this device. */
    > + struct resource *parent_resource;
    > +
    > /* Summary of all memory block states. */
    > unsigned long nb_mb_state[VIRTIO_MEM_MB_STATE_COUNT];
    > #define VIRTIO_MEM_NB_OFFLINE_THRESHOLD 10
    > @@ -1741,6 +1744,44 @@ static int virtio_mem_init(struct virtio_mem *vm)
    > return 0;
    > }
    >
    > +static int virtio_mem_create_resource(struct virtio_mem *vm)
    > +{
    > + /*
    > + * When force-unloading the driver and removing the device, we
    > + * could have a garbage pointer. Duplicate the string.
    > + */
    > + const char *name = kstrdup(dev_name(&vm->vdev->dev), GFP_KERNEL);
    > +
    > + if (!name)
    > + return -ENOMEM;
    > +
    > + vm->parent_resource = __request_mem_region(vm->addr, vm->region_size,
    > + name, IORESOURCE_SYSTEM_RAM);
    > + if (!vm->parent_resource) {
    > + kfree(name);
    > + dev_warn(&vm->vdev->dev, "could not reserve device region\n");
    > + return -EBUSY;
    > + }
    > +
    > + /* The memory is not actually busy - make add_memory() work. */
    > + vm->parent_resource->flags &= ~IORESOURCE_BUSY;
    > + return 0;
    > +}
    > +
    > +static void virtio_mem_delete_resource(struct virtio_mem *vm)
    > +{
    > + const char *name;
    > +
    > + if (!vm->parent_resource)
    > + return;
    > +
    > + name = vm->parent_resource->name;
    > + release_resource(vm->parent_resource);
    > + kfree(vm->parent_resource);
    > + kfree(name);
    > + vm->parent_resource = NULL;
    > +}
    > +
    > static int virtio_mem_probe(struct virtio_device *vdev)
    > {
    > struct virtio_mem *vm;
    > @@ -1770,11 +1811,16 @@ static int virtio_mem_probe(struct virtio_device *vdev)
    > if (rc)
    > goto out_del_vq;
    >
    > + /* create the parent resource for all memory */
    > + rc = virtio_mem_create_resource(vm);
    > + if (rc)
    > + goto out_del_vq;
    > +
    > /* register callbacks */
    > vm->memory_notifier.notifier_call = virtio_mem_memory_notifier_cb;
    > rc = register_memory_notifier(&vm->memory_notifier);
    > if (rc)
    > - goto out_del_vq;
    > + goto out_del_resource;
    > rc = register_virtio_mem_device(vm);
    > if (rc)
    > goto out_unreg_mem;
    > @@ -1788,6 +1834,8 @@ static int virtio_mem_probe(struct virtio_device *vdev)
    > return 0;
    > out_unreg_mem:
    > unregister_memory_notifier(&vm->memory_notifier);
    > +out_del_resource:
    > + virtio_mem_delete_resource(vm);
    > out_del_vq:
    > vdev->config->del_vqs(vdev);
    > out_free_vm:
    > @@ -1848,6 +1896,8 @@ static void virtio_mem_remove(struct virtio_device *vdev)
    > vm->nb_mb_state[VIRTIO_MEM_MB_STATE_ONLINE_PARTIAL] ||
    > vm->nb_mb_state[VIRTIO_MEM_MB_STATE_ONLINE_MOVABLE])
    > dev_warn(&vdev->dev, "device still has system memory added\n");
    > + else
    > + virtio_mem_delete_resource(vm);
    >
    > /* remove all tracking data - no locking needed */
    > vfree(vm->mb_state);
    > --

    Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>

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