[Qemu-devel] question about handling overlapping memory when add region in qemu

[jack.chen]

Hello ,in kvm_set_phys_mem,I am confused about the following codes:
delta = TARGET_PAGE_ALIGN(size) - size;
    if (delta > size) {
        return;
    }
    start_addr += delta;
    size -= delta;
    size &= TARGET_PAGE_MASK;

why start_addr need to add delta,and why size sub delta,in my own
opinion,if size +=delta ,I can understand,but i do not know why
sub??thanks in advance!!