On Thu, 23 Sep 2021, 09:11 FMDF, <fmdefrance...@gmail.com> wrote: > On Wed, 22 Sep 2021, 08:22 Ruben Safir, <ru...@mrbrklyn.com> wrote: > >> What is this for? >> >> efivarfs on /sys/firmware/efi/efivars type efivarfs >> >> why would the OS need to know anything about the UEFI >> boot loader once it is up and running? >> > > I think you are still making confusion: UEFI bootloaders and UEFI are two > different entities. > > UEFI bootloaders (like Grub2) serve the purpose to locate, pass kernel > options and platform information to the kernel that themselves are going > to boot. > > Instead the UEFI is an interface between the running OS and the platform > firmware. > > UEFI defines two types of services: boot services and runtime services. > > After booting is done, via UEFI boot services and eventually UEFI > bootloaders, the OS does not need anymore the bootloader and the UEFI boot > services. > > Instead the OS needs UEFI runtime services to talk to the platform > firmware. For example, if OS cannot talk to the platform via UEFI, it > cannot even shutdown the system (obviously there is much more than simply > shutting down). How can an OS know that you've attached a plug and play > device if it cannot talk to the platform firmware? > > Fabio >
For sake of completeness and for better understanding that OS need UEFI, but not necessarily EFI bootloaders, please read the following document: https://www.kernel.org/doc/html/latest/admin-guide/efi-stub.html Linux can boot without bootloaders, but it still needs to use UEFI at runtime. Fabio >
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