CPU Stats With Variable And All

I have a dashboard using Prometheus as my data source and a processor variable that gets all of the processors I am looking for. If I use Explore with this:

cpu_usage_user{host=“server”}

I get each CPU and all of the CPU usage for user. In my visual on the dashboard I use the following query:

cpu_usage_user{host=“$hostname”, cpu=“$processor”}

On my drop down variable for processor, if I pick say cpu0 it shows data. If I select all it show no data. What am I missing in either the query or the variable and where should I make my change?