static void vhost_dev_unassign_memory(struct vhost_dev *dev, uint64_t start_addr, uint64_t size) { int from, to, n = dev->mem->nregions; /* Track overlapping/split regions for sanity checking. */ int overlap_start = 0, overlap_end = 0, overlap_middle = 0, split = 0; for (from = 0, to = 0; from < n; ++from, ++to) { struct vhost_memory_region *reg = dev->mem->regions + to; uint64_t reglast; uint64_t memlast; uint64_t change; /* clone old region */ if (to != from) { memcpy(reg, dev->mem->regions + from, sizeof *reg); } /* No overlap is simple */ if (!ranges_overlap(reg->guest_phys_addr, reg->memory_size, start_addr, size)) { continue; } /* Split only happens if supplied region * is in the middle of an existing one. Thus it can not * overlap with any other existing region. */ assert(!split); reglast = range_get_last(reg->guest_phys_addr, reg->memory_size); memlast = range_get_last(start_addr, size); /* Remove whole region */ if (start_addr <= reg->guest_phys_addr && memlast >= reglast) { --dev->mem->nregions; --to; assert(to >= 0); ++overlap_middle; continue; } /* Shrink region */ if (memlast >= reglast) { reg->memory_size = start_addr - reg->guest_phys_addr; assert(reg->memory_size); assert(!overlap_end); ++overlap_end; continue; } /* Shift region */ if (start_addr <= reg->guest_phys_addr) { change = memlast + 1 - reg->guest_phys_addr; reg->memory_size -= change; reg->guest_phys_addr += change; reg->userspace_addr += change; assert(reg->memory_size); assert(!overlap_start); ++overlap_start; continue; } /* This only happens if supplied region * is in the middle of an existing one. Thus it can not * overlap with any other existing region. */ assert(!overlap_start); assert(!overlap_end); assert(!overlap_middle); /* Split region: shrink first part, shift second part. */ memcpy(dev->mem->regions + n, reg, sizeof *reg); reg->memory_size = start_addr - reg->guest_phys_addr; assert(reg->memory_size); change = memlast + 1 - reg->guest_phys_addr; reg = dev->mem->regions + n; reg->memory_size -= change; assert(reg->memory_size); reg->guest_phys_addr += change; reg->userspace_addr += change; /* Never add more than 1 region */ assert(dev->mem->nregions == n); ++dev->mem->nregions; ++split; } }