On Thu, 23 Sep 2021, 09:22 FMDF, <fmdefrance...@gmail.com> wrote: > 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 >
While at this, please read also: https://www.kernel.org/doc/html/latest/arm/uefi.html https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface
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