On Aug 1, 2022, at 3:50 PM, Axel Rasmussen <axelrasmussen@xxxxxxxxxx> wrote: > ⚠ External Email > > On Mon, Aug 1, 2022 at 12:53 PM Nadav Amit <namit@xxxxxxxxxx> wrote: >> On Aug 1, 2022, at 10:13 AM, Axel Rasmussen <axelrasmussen@xxxxxxxxxx> wrote: > > Ah, that I think is more or less what my series already proposes, if I > understand you correctly. > > The usage is: > > fd = open(/dev/userfaultfd) /* This FD is only useful for creating new > userfaultfds */ > uffd = ioctl(fd, USERFAULTFD_IOC_NEW) /* Now you get a real uffd */ > close(fd); /* No longer needed now that we have a real uffd */ > > /* Use uffd to register, COPY, CONTINUE, whatever */ > > One thing we could do now or in the future is extend > USERFAULTFD_IOC_NEW to take a pid as an argument, to support creating > uffds for remote processes. > > > > And then we get the benefit of permissions for /dev nodes working very > naturally - they default to root, but can be configured by the > sysadmin via chown/chmod, or udev rules, or whatever. Oh. Stupid me. Then yes, using the /dev/userfaultfd is in line with other usage models, such as KVM. And reading from each file descriptor is indeed providing different output.
