* Dave Hansen via Libc-alpha:
Our system calls are *REALLY* fast. We can even do a vsyscall for this
if we want to get the overhead down near zero. Userspace can also cache
the "I did the prctl()" state in thread-local storage if it wants to
avoid the syscall.
Why can't userspace look at XCR0 to make the decision?
And we added an interface for querying x86 CPU features to glibc 2.33
which is completely incompatible with this because it assumes that CPU
features do not change during the lifetime of a process. 8-(
Thanks,
Florian