[Linux-PowerEdge] FYI: BIOS Update fails due to CONFIG_STRICT_DEVMEM=y in linux kernel 4.16+

Stephen Dowdy sdowdy at ucar.edu
Thu Jul 12 15:40:54 CDT 2018


Update:  adding 'iomem=relaxed' to the kernel bootparams allows 'biosie' (from the BIOS*.BIN DUPkit) to update the BIOS.

The docs on this suck, though:

.../src/linux-source-4.16/Documentation# sed -ne '/iomem=/,/^$/p'  ./admin-guide/kernel-parameters.txt
         iomem=          Disable strict checking of access to MMIO memory
                 strict  regions from userspace.
                 relaxed

No indications of the risks involved (okay, i presume this is a little better than all /dev/mem, as it would still immediately protect against memory scraping sensitive user process data and such, but still lets a potential cracker control/manipulate devices)

But unless i run that way always, rebooting an alternate grub line just to BIOS update adds an extra reboot.
(the goal is to not have to sit at the console, take long periods in lifecycle controller, ... or do multiple reboot hacks)
(I'm getting the feeling there's going to be no easy workaround anymore past Kernel 4.16 because the SMBIOS table is iomapped outide 1MB)

--stephen

-- 
Stephen Dowdy  -  Systems Administrator  -  NCAR/RAL
303.497.2869   -  sdowdy at ucar.edu        -  http://www.ral.ucar.edu/~sdowdy/



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