Re: [PATCH v1 1/3] kernel/resource: make walk_system_ram_res() find all busy IORESOURCE_SYSTEM_RAM resources

[David Hildenbrand]

On 24.03.21 12:18, Oscar Salvador wrote:
> On Mon, Mar 22, 2021 at 05:01:58PM +0100, David Hildenbrand wrote:
> > It used to be true that we can have busy system RAM only on the first level
> > in the resourc tree. However, this is no longer holds for driver-managed
> > system RAM (i.e., added via dax/kmem and virtio-mem), which gets added on
> > lower levels.
>
> Let me ask some rookie questions:
>
> What does "busy" term stand for here?

IORESOURCE_BUSY - here: actually added, not just some reserved range / container.


> Why resources coming from virtio-mem are added at a lower levels?

Some information can be had from ebf71552bb0e690cad523ad175e8c4c89a33c333

commit ebf71552bb0e690cad523ad175e8c4c89a33c333
Author: David Hildenbrand <david@xxxxxxxxxx>
Date:   Thu May 7 16:01:35 2020 +0200

    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
            [...]



For dax/kmem it comes naturally due to the "Persistent Memory" and
device parent resources like:

            140000000-33fffffff : Persistent Memory
              140000000-1481fffff : namespace0.0
              150000000-33fffffff : dax0.0
                150000000-33fffffff : System RAM (kmem)
            3280000000-32ffffffff : PCI Bus 0000:00


Thanks

--
Thanks,

David / dhildenb