From 37aee82c213d352dccb850dc4228dda2e7e591b1 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Thu, 20 Jun 2024 09:10:49 +0200 Subject: x86/efi: Drop support for fake EFI memory maps Between kexec and confidential VM support, handling the EFI memory maps correctly on x86 is already proving to be rather difficult (as opposed to other EFI architectures which manage to never modify the EFI memory map to begin with) EFI fake memory map support is essentially a development hack (for testing new support for the 'special purpose' and 'more reliable' EFI memory attributes) that leaked into production code. The regions marked in this manner are not actually recognized as such by the firmware itself or the EFI stub (and never have), and marking memory as 'more reliable' seems rather futile if the underlying memory is just ordinary RAM. Marking memory as 'special purpose' in this way is also dubious, but may be in use in production code nonetheless. However, the same should be achievable by using the memmap= command line option with the ! operator. EFI fake memmap support is not enabled by any of the major distros (Debian, Fedora, SUSE, Ubuntu) and does not exist on other architectures, so let's drop support for it. Acked-by: Borislav Petkov (AMD) Acked-by: Dan Williams Signed-off-by: Ard Biesheuvel --- Documentation/admin-guide/kernel-parameters.txt | 21 --------------------- 1 file changed, 21 deletions(-) (limited to 'Documentation') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 11e57ba2985c..90c64525e7e1 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1450,27 +1450,6 @@ you are really sure that your UEFI does sane gc and fulfills the spec otherwise your board may brick. - efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI,X86,EARLY] - Add arbitrary attribute to specific memory range by - updating original EFI memory map. - Region of memory which aa attribute is added to is - from ss to ss+nn. - - If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 - is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) - attribute is added to range 0x100000000-0x180000000 and - 0x10a0000000-0x1120000000. - - If efi_fake_mem=8G@9G:0x40000 is specified, the - EFI_MEMORY_SP(0x40000) attribute is added to - range 0x240000000-0x43fffffff. - - Using this parameter you can do debugging of EFI memmap - related features. For example, you can do debugging of - Address Range Mirroring feature even if your box - doesn't support it, or mark specific memory as - "soft reserved". - efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT that is to be dynamically loaded by Linux. If there are multiple variables with the same name but with different -- cgit v1.2.3-70-g09d2