David Hildenbrand <da...@redhat.com> wrote:
> Already when starting QEMU we perform one system reset that ends up
> triggering virtio_mem_unplug_all() with no actual memory plugged yet.
> That, in turn will trigger ram_block_discard_range() and perform some
> other actions that are not required in that case.
>
> Let's optimize virtio_mem_unplug_all() for the case that no memory is
> plugged. This will be beneficial for x-ignore-shared support as well.
>
> Tested-by: Mario Casquero <mcasq...@redhat.com>
> Signed-off-by: David Hildenbrand <da...@redhat.com>
It works, so ...
Reviewed-by: Juan Quintela <quint...@redhat.com>
> RAMBlock *rb = vmem->memdev->mr.ram_block;
>
> - if (virtio_mem_is_busy()) {
> - return -EBUSY;
> - }
> -
> - if (ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb))) {
> - return -EBUSY;
> - }
> - virtio_mem_notify_unplug_all(vmem);
> -
> - bitmap_clear(vmem->bitmap, 0, vmem->bitmap_size);
> if (vmem->size) {
> + if (virtio_mem_is_busy()) {
> + return -EBUSY;
I see that the only way that virtio_men_is_busy() is true is if we are
in the middle of a migration. In the case that vmem is 0, we don't
care. So we are good.
> + }
> + if (ram_block_discard_range(rb, 0, qemu_ram_get_used_length(rb))) {
> + return -EBUSY;
> + }
Nothing to discard, so also good.
> + virtio_mem_notify_unplug_all(vmem);
Nothing to notify, so also good.
> + bitmap_clear(vmem->bitmap, 0, vmem->bitmap_size);
> vmem->size = 0;
> notifier_list_notify(&vmem->size_change_notifiers, &vmem->size);
> }
> +
> trace_virtio_mem_unplugged_all();
> virtio_mem_resize_usable_region(vmem, vmem->requested_size, true);
> return 0;
Once that we are here. Do you remember _why_ do we allow virtio-mem
plug/unplug in the middle of a migration.
We forbid to plug/unplug everything else. Why do we need to plug/unplug
virtio-mem during migration?
Thanks, Juan.
