OSDev.org

ok, this is very very specific and I got intel manual in front of me...

The second bit in a page table entry is user supervisor bit...

for kernel should I set that bit to supervisor, which is 0...

my logic... kernel/user isolation is obvious, but in the case of syscall, kernel code should
be able to access kernel data segments on behalf of user... so

that bit should be set to zero for kernel...

Is this right?

You don't want user code to be able to access kernel data, so the bit should be set to 0. As you say, the system call access data on behalf of the user, if necessary.