[libvirt-users] SSD Trim needed? Physical Block Device Keep Track Of Guest FS Blocks?

I am trying to figure out if a SSD drive needs to receive trim commands from the KVM guest filesystem(strictly Linux ext4 in this case).... When a file is deleted inside a KVM guest(ext4 and raw image)....If a SSD is the underlying block device that the KVM raw disk image resides on, does the SDD drive need to know which block(s) are marked for reuse within the raw image?  Or is it since the Guest raw image is a container that the physical hard drive has no concern about the filesystem blocks within the Guest? Meaning the physical disk would only be concerned with the image itself as a whole...such as if the whole image was deleted? Thanks, -Darin