Re: [PATCH v1 3/5] memory-device: Support big alignment requirements

[Pankaj Gupta <pankaj.gupta.linux@gmail.com>]

> Let's warn instead of bailing out - the worst thing that can happen is
> that we'll fail hot/coldplug later. The user got warned, and this should
> be rare.
>
> This will be necessary for memory devices with rather big (user-defined)
> alignment requirements - say a virtio-mem device with a 2G block size -
> which will become important, for example, when supporting vfio in the
> future.
>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Wei Yang <richardw.yang@linux.intel.com>
> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  hw/mem/memory-device.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/hw/mem/memory-device.c b/hw/mem/memory-device.c
> index 4bc9cf0917..8a736f1a26 100644
> --- a/hw/mem/memory-device.c
> +++ b/hw/mem/memory-device.c
> @@ -119,9 +119,10 @@ static uint64_t memory_device_get_free_addr(MachineState *ms,
>
>      /* start of address space indicates the maximum alignment we expect */
>      if (!QEMU_IS_ALIGNED(range_lob(&as), align)) {
> -        error_setg(errp, "the alignment (0x%" PRIx64 ") is not supported",
> -                   align);
> -        return 0;
> +        warn_report("the alignment (0x%" PRIx64 ") exceeds the expected"
> +                    " maximum alignment, memory will get fragmented and not"
> +                    " all 'maxmem' might be usable for memory devices.",
> +                    align);
>      }
>
>      memory_device_check_addable(ms, size, &err);
> @@ -151,7 +152,7 @@ static uint64_t memory_device_get_free_addr(MachineState *ms,
>              return 0;
>          }
>      } else {
> -        if (range_init(&new, range_lob(&as), size)) {
> +        if (range_init(&new, QEMU_ALIGN_UP(range_lob(&as), align), size)) {
>              error_setg(errp, "can't add memory device, device too big");
>              return 0;
>          }

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