A fix for a bug with restartable sequences and KVM.  KVM's handling
of TIF_NOTIFY_RESUME, e.g. for task migration, clears the flag without
informing rseq and leads to stale data in userspace's rseq struct.

I'm sending this as a separate pull request since it's not code
that I usually touch.  In particular, patch 2 ("entry: rseq: Call
rseq_handle_notify_resume() in tracehook_notify_resume()") is just a
cleanup to try and make future bugs less likely.  If you prefer this to
be sent via Thomas and only in 5.16, please speak up.
KVM: selftests: Remove __NR_userfaultfd syscall fallback

Revert the __NR_userfaultfd syscall fallback added for KVM selftests now
that x86's unistd_{32,63}.h overrides are under uapi/ and thus not in
KVM selftests' search path, i.e. now that KVM gets x86 syscall numbers
from the installed kernel headers.

No functional change intended.

Reviewed-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210901203030.1292304-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
1 file changed