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x86/startup_64: Defer assignment of 5-level paging global variables 

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@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240227151907.387873-13-ardb+git@google.com
This commit is contained in:
Ard Biesheuvel 2024-02-27 16:19:10 +01:00 committed by Borislav Petkov (AMD)
parent dada858706
commit 63bed96604
2 changed files with 15 additions and 31 deletions
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2
arch/x86/include/asm/pgtable_64_types.h
View File

@ -21,9 +21,9 @@ typedef unsigned long pgprotval_t;
typedef struct { pteval_t pte; } pte_t;
typedef struct { pmdval_t pmd; } pmd_t;
#ifdef CONFIG_X86_5LEVEL
extern unsigned int __pgtable_l5_enabled;
#ifdef CONFIG_X86_5LEVEL
#ifdef USE_EARLY_PGTABLE_L5
/*
* cpu_feature_enabled() is not available in early boot code.

44
arch/x86/kernel/head64.c
View File

@ -23,6 +23,7 @@
#include <linux/pgtable.h>
#include <asm/asm.h>
#include <asm/page_64.h>
#include <asm/processor.h>
#include <asm/proto.h>
#include <asm/smp.h>
@ -68,24 +69,11 @@ unsigned long vmemmap_base __ro_after_init = __VMEMMAP_BASE_L4;
EXPORT_SYMBOL(vmemmap_base);
#endif
#ifdef CONFIG_X86_5LEVEL
static void __head *fixup_pointer(void *ptr, unsigned long physaddr)
static inline bool check_la57_support(void)
{
return ptr - (void *)_text + (void *)physaddr;
}
if (!IS_ENABLED(CONFIG_X86_5LEVEL))
return false;
static unsigned long __head *fixup_long(void *ptr, unsigned long physaddr)
{
return fixup_pointer(ptr, physaddr);
}
static unsigned int __head *fixup_int(void *ptr, unsigned long physaddr)
{
return fixup_pointer(ptr, physaddr);
}
static bool __head check_la57_support(unsigned long physaddr)
{
/*
* 5-level paging is detected and enabled at kernel decompression
* stage. Only check if it has been enabled there.
@ -93,21 +81,8 @@ static bool __head check_la57_support(unsigned long physaddr)
if (!(native_read_cr4() & X86_CR4_LA57))
return false;
*fixup_int(&__pgtable_l5_enabled, physaddr) = 1;
*fixup_int(&pgdir_shift, physaddr) = 48;
*fixup_int(&ptrs_per_p4d, physaddr) = 512;
*fixup_long(&page_offset_base, physaddr) = __PAGE_OFFSET_BASE_L5;
*fixup_long(&vmalloc_base, physaddr) = __VMALLOC_BASE_L5;
*fixup_long(&vmemmap_base, physaddr) = __VMEMMAP_BASE_L5;
return true;
}
#else
static bool __head check_la57_support(unsigned long physaddr)
{
return false;
}
#endif
static unsigned long __head sme_postprocess_startup(struct boot_params *bp, pmdval_t *pmd)
{
@ -171,7 +146,7 @@ unsigned long __head __startup_64(unsigned long physaddr,
bool la57;
int i;
la57 = check_la57_support(physaddr);
la57 = check_la57_support();
/* Is the address too large? */
if (physaddr >> MAX_PHYSMEM_BITS)
@ -456,6 +431,15 @@ asmlinkage __visible void __init __noreturn x86_64_start_kernel(char * real_mode
(__START_KERNEL & PGDIR_MASK)));
BUILD_BUG_ON(__fix_to_virt(__end_of_fixed_addresses) <= MODULES_END);
if (check_la57_support()) {
__pgtable_l5_enabled = 1;
pgdir_shift = 48;
ptrs_per_p4d = 512;
page_offset_base = __PAGE_OFFSET_BASE_L5;
vmalloc_base = __VMALLOC_BASE_L5;
vmemmap_base = __VMEMMAP_BASE_L5;
}
cr4_init_shadow();
/* Kill off the identity-map trampoline */