panic with AMD EPYC 7313P on 10.0_BETA

[Mark Davies <mark%ecs.vuw.ac.nz@localhost>]

Trying to boot a Dell Power Edge R6515 that has an AMD EPYC 7313P  with 
10.0_BETA from a couple of day ago panics with:


panic: kernel diagnostic assertion "rcr4() & CR4_SMAP" failed: file 
"...sys/arch/x86/x86/patch.c"

backtrace of:
   vpanic()
   kern_assert()
   x86_patch()
   cpu_boot_secondary_processors()
   main()


Any suggestions what's going on and how to fix?

cheers
mark