Re: [PATCH v3 06/19] x86/startup_64: Drop global variables keeping track of LA57 state

[Borislav Petkov]

On Fri, Feb 09, 2024 at 01:55:02PM +0000, Ard Biesheuvel wrote:
> I was trying to get rid of global variable assignments and accesses
> from the 1:1 mapping, but since we cannot get rid of those entirely,
> we might just keep __pgtable_l5_enabled but use RIP_REL_REF() in the
> accessors, and move the assignment to the asm startup code.

Yeah.

>    asm(ALTERNATIVE_TERNARY(
>        "movq %%cr4, %[reg] \n\t btl %[la57], %k[reg]" CC_SET(c),
>        %P[feat], "stc", "clc")
>        : [reg] "=r" (r), CC_OUT(c) (ret)
>        : [feat] "i" (X86_FEATURE_LA57),
>          [la57] "i" (X86_CR4_LA57_BIT)
>        : "cc");

Creative :)

> but we'd still have two versions in that case.

Yap. RIP_REL_REF() ain't too bad ...

Thx.

-- 
Regards/Gruss,
    Boris.

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