diff options
Diffstat (limited to '')
| -rw-r--r-- | arch/x86/boot/compressed/head_64.S | 45 |
1 files changed, 4 insertions, 41 deletions
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index cd6e3e175389..8730b1d58e2b 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -387,10 +387,6 @@ SYM_CODE_START(startup_64) * For the trampoline, we need the top page table to reside in lower * memory as we don't have a way to load 64-bit values into CR3 in * 32-bit mode. - * - * We go though the trampoline even if we don't have to: if we're - * already in a desired paging mode. This way the trampoline code gets - * tested on every boot. */ /* Make sure we have GDT with 32-bit code segment */ @@ -526,8 +522,7 @@ SYM_FUNC_END(.Lrelocated) * * Return address is at the top of the stack (might be above 4G). * The first argument (EDI) contains the 32-bit addressable base of the - * trampoline memory. A non-zero second argument (ESI) means that the - * trampoline needs to enable 5-level paging. + * trampoline memory. */ .section ".rodata", "a", @progbits SYM_CODE_START(trampoline_32bit_src) @@ -579,25 +574,10 @@ SYM_CODE_START(trampoline_32bit_src) btrl $X86_CR0_PG_BIT, %eax movl %eax, %cr0 - /* Check what paging mode we want to be in after the trampoline */ - testl %esi, %esi - jz 1f - - /* We want 5-level paging: don't touch CR3 if it already points to 5-level page tables */ - movl %cr4, %eax - testl $X86_CR4_LA57, %eax - jnz 3f - jmp 2f -1: - /* We want 4-level paging: don't touch CR3 if it already points to 4-level page tables */ - movl %cr4, %eax - testl $X86_CR4_LA57, %eax - jz 3f -2: /* Point CR3 to the trampoline's new top level page table */ leal TRAMPOLINE_32BIT_PGTABLE_OFFSET(%edi), %eax movl %eax, %cr3 -3: + /* Set EFER.LME=1 as a precaution in case hypervsior pulls the rug */ movl $MSR_EFER, %ecx rdmsr @@ -606,26 +586,9 @@ SYM_CODE_START(trampoline_32bit_src) jc 1f wrmsr 1: -#ifdef CONFIG_X86_MCE - /* - * Preserve CR4.MCE if the kernel will enable #MC support. - * Clearing MCE may fault in some environments (that also force #MC - * support). Any machine check that occurs before #MC support is fully - * configured will crash the system regardless of the CR4.MCE value set - * here. - */ + /* Toggle CR4.LA57 */ movl %cr4, %eax - andl $X86_CR4_MCE, %eax -#else - movl $0, %eax -#endif - - /* Enable PAE and LA57 (if required) paging modes */ - orl $X86_CR4_PAE, %eax - testl %esi, %esi - jz 1f - orl $X86_CR4_LA57, %eax -1: + btcl $X86_CR4_LA57_BIT, %eax movl %eax, %cr4 /* Enable paging again. */ |