Hi, Charlie Although this patchset has been merged I still have some questions about this patchset. Because it breaks regular mmap if address >= 38 bits on sv48 / sv57 capable systems like qemu. For example, If a userspace program wants to mmap an anonymous page to addr=(1<<45) on an sv48 capable system, it will fail and kernel will mmaped to another sv39 address since it does not meet the requirement to use sv48 as you wrote: > else if ((((_addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \ > mmap_end = VA_USER_SV48; \ > else \ > mmap_end = VA_USER_SV39; \ Then, How can a userspace program create a mmap with a hint if the address >= (1<<38) after your patch without MAP_FIXED? The only way to do this is to pass a hint >= (1<<47) on mmap syscall then kernel will return a random address in sv48 address space but the hint address gets lost. I think this violate the principle of mmap syscall as kernel should take the hint and attempt to create the mapping there. I don't think patching in this way is right. However, if we only revert this patch, some programs relying on mmap to return address with effective bits <= 48 will still be an issue and it might expand to other ISAs if they implement larger virtual address space like RISC-V sv57. A better way to solve this might be adding a MAP_48BIT flag to mmap like MAP_32BIT has been introduced for decades. Thanks, Yangyu Chen
