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#include <asm/processor.h>
/*
* __force_order is used by special_insns.h asm code to force instruction
* serialization.
*
* It is not referenced from the code, but GCC < 5 with -fPIE would fail
* due to an undefined symbol. Define it to make these ancient GCCs work.
*/
unsigned long __force_order;
struct paging_config {
unsigned long trampoline_start;
unsigned long l5_required;
};
struct paging_config paging_prepare(void)
{
struct paging_config paging_config = {};
/*
* Check if LA57 is desired and supported.
*
* There are two parts to the check:
* - if the kernel supports 5-level paging: CONFIG_X86_5LEVEL=y
* - if the machine supports 5-level paging:
* + CPUID leaf 7 is supported
* + the leaf has the feature bit set
*
* That's substitute for boot_cpu_has() in early boot code.
*/
if (IS_ENABLED(CONFIG_X86_5LEVEL) &&
native_cpuid_eax(0) >= 7 &&
(native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31)))) {
paging_config.l5_required = 1;
}
return paging_config;
}
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