Add README-epel.md with instructions for enabling PSI support

Signed-off-by: Michel Alexandre Salim <salimma@fedoraproject.org>

README-epel.md

@@ -0,0 +1,12 @@
+# Note for EPEL users
+
+The stock EL8 (RHEL/CentOS/CentOS Stream) kernel has PSI support compiled 
+into the kernel but disabled by default.
+
+You will need to pass `psi=1` on the kernel command line, see
+https://facebookmicrosites.github.io/psi/docs/overview.html#prerequisites
+
+To persist, add this to `/etc/default/grub` to the `GRUB_CMDLINE_LINUX`
+string and rebuild the GRUB config by running this as root:
+
+`grub2-mkconfig -o /etc/grub2-efi.cfg`

rust-below.spec

@@ -17,7 +17,7 @@
 
 Name:           rust-%{crate}
 Version:        0.2.0
-Release:        3%{?dist}
+Release:        4%{?dist}
 Summary:        Interactive tool to view and record historical system data
 
 # Upstream license specification: Apache-2.0
@@ -36,6 +36,8 @@ Source3:        %{forgeurl}/raw/%{commit}/README.md#/README-upstream.md
 # vendored dependencies for EPEL
 # update with ./update-vendor-tarball.sh after bumping the specfile version
 Source4:        %{crate}-%{version}-vendor.tar.gz
+# EPEL specific doc
+Source5:        README-epel.md
 
 ExclusiveArch:  %{rust_arches}
 
@@ -87,6 +89,9 @@ Recommends:     logrotate
 %files       -n %{crate}
 %license LICENSE
 %doc README.md docs
+%if 0%{?el8}
+%doc README-epel.md
+%endif
 %attr(755, root, root) %{_bindir}/%{crate}
 %{_unitdir}/%{crate}.service
 %config(noreplace) %{_sysconfdir}/logrotate.d/%{crate}.conf
@@ -117,6 +122,10 @@ cp -p %{SOURCE3} README.md
 %cargo_generate_buildrequires
 %endif
 
+%if 0%{?el8}
+cp -p %{SOURCE5} README-epel.md
+%endif
+
 %build
 %cargo_build
 
@@ -133,6 +142,9 @@ install -d -m1777 %{buildroot}%{_localstatedir}/log/%{crate}
 %endif
 
 %changelog
+* Thu Jul  1 2021 Michel Alexandre Salim <salimma@fedoraproject.org> - 0.2.0-4
+- Add README-epel.md with instructions for enabling PSI support
+
 * Wed Jun 30 2021 Davide Cavalca <dcavalca@fedoraproject.org> - 0.2.0-3
 - Add vendored dependencies for EPEL and make it build there
 - Exclude s390x for the EPEL build for now due to an upstream issue