How to get CMU small caps as a separate font?

Question

CMU bold small capitals work for me with \usepackage[T1]{fontenc} but not with \usepackage{fontspec}. Is there a way to get a separate CMU font that only has small capitals? When I buy fonts they come with separate files for small capitals and that works fine with fontspec.

Edit

\documentclass{report}
\usepackage{fontspec}

\setmainfont{Latin Modern Roman 10 Regular}[
    BoldFeatures = {SmallCapsFont = {CMU Serif Bold}},
    SmallCapsFont = Latin Modern Roman Caps]

\begin{document}

Roman. \textbf{Bold.} \textsc{Small capitals.} 
\textbf{\textsc{Bold small capitals.}}

\end{document}

Answer 1

You have to set the features for small caps in a boldface context.

\documentclass{report}
\usepackage{fontspec}

\setmainfont{Latin Modern Roman}[
  BoldFeatures = {
    SmallCapsFont = CMU Serif Bold Extended Roman,
    SmallCapsFeatures={Letters=SmallCaps},
  },
  SmallCapsFont = Latin Modern Roman Caps,
]

\begin{document}

Roman. \textbf{Bold.} \textsc{Small capitals.}
\textbf{\textsc{Bold small capitals.}}

\end{document}

Answer 2

Latin Modern Roman font does not include a bold small caps variant.

You can use the CMR Unicode font.

This should work with both xelatex and lualatex:

\documentclass{article}    
\usepackage{fontspec}    
\setmainfont{CMU Serif}    
\begin{document}    
\scshape small caps \bfseries bold small caps    
\end{document}