Re: [PATCH v2 08/14] s390x/s390-stattrib-kvm: prepare for memory devices and sparse memory layouts

[Thomas Huth <thuth@redhat.com>]

On 08/10/2024 12.54, David Hildenbrand wrote:
> With memory devices, we will have storage attributes for memory that
> exceeds the initial ram size. Further, we can easily have memory holes,
> for which there (currently) are no storage attributes.
> 
> In particular, with memory holes, KVM_S390_SET_CMMA_BITS will fail to set
> some storage attributes.
> 
> So let's do it like we handle storage keys migration, relying on
> guest_phys_blocks_append(). However, in contrast to storage key
> migration, we will handle it on the migration destination.
> 
> This is a preparation for virtio-mem support. Note that ever since the
> "early migration" feature was added (x-early-migration), the state
> of device blocks (plugged/unplugged) is migrated early such that
> guest_phys_blocks_append() will properly consider all currently plugged
> memory blocks and skip any unplugged ones.
> 
> In the future, we should try getting rid of the large temporary buffer
> and also not send any attributes for any memory holes, just so they
> get ignored on the destination.
> 
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>   hw/s390x/s390-stattrib-kvm.c | 67 +++++++++++++++++++++++-------------
>   1 file changed, 43 insertions(+), 24 deletions(-)

Reviewed-by: Thomas Huth <thuth@redhat.com>