Re: [PATCH v4 04/11] x86/startup_64: Defer assignment of 5-level paging global variables

[Borislav Petkov]

On Tue, Feb 13, 2024 at 01:41:48PM +0100, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@xxxxxxxxxx>
> 
> Assigning the 5-level paging related global variables from the earliest
> C code using explicit references that use the 1:1 translation of memory
> is unnecessary, as the startup code itself does not rely on them to
> create the initial page tables, and this is all it should be doing. So
> defer these assignments to the primary C entry code that executes via
> the ordinary kernel virtual mapping.
> 
> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> ---
>  arch/x86/kernel/head64.c | 44 +++++++-------------
>  1 file changed, 14 insertions(+), 30 deletions(-)

Whoops:

arch/x86/kernel/head64.c: In function ‘x86_64_start_kernel’:
arch/x86/kernel/head64.c:442:17: error: ‘__pgtable_l5_enabled’ undeclared (first use in this function); did you mean ‘pgtable_l5_enabled’?
  442 |                 __pgtable_l5_enabled    = 1;
      |                 ^~~~~~~~~~~~~~~~~~~~
      |                 pgtable_l5_enabled
arch/x86/kernel/head64.c:442:17: note: each undeclared identifier is reported only once for each function it appears in
make[4]: *** [scripts/Makefile.build:243: arch/x86/kernel/head64.o] Error 1
make[3]: *** [scripts/Makefile.build:481: arch/x86/kernel] Error 2
make[2]: *** [scripts/Makefile.build:481: arch/x86] Error 2
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [/mnt/kernel/kernel/2nd/linux/Makefile:1921: .] Error 2
make: *** [Makefile:240: __sub-make] Error 2


-- 
Regards/Gruss,
    Boris.

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