diff options
Diffstat (limited to 'arch/x86/boot/compressed/head_64.S')
| -rw-r--r-- | arch/x86/boot/compressed/head_64.S | 21 |
1 files changed, 16 insertions, 5 deletions
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 64037895b085..fafb75c6c592 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -358,8 +358,11 @@ ENTRY(startup_64) * paging_prepare() sets up the trampoline and checks if we need to * enable 5-level paging. * - * Address of the trampoline is returned in RAX. - * Non zero RDX on return means we need to enable 5-level paging. + * paging_prepare() returns a two-quadword structure which lands + * into RDX:RAX: + * - Address of the trampoline is returned in RAX. + * - Non zero RDX means trampoline needs to enable 5-level + * paging. * * RSI holds real mode data and needs to be preserved across * this function call. @@ -565,7 +568,7 @@ adjust_got: * * RDI contains the return address (might be above 4G). * ECX contains the base address of the trampoline memory. - * Non zero RDX on return means we need to enable 5-level paging. + * Non zero RDX means trampoline needs to enable 5-level paging. */ ENTRY(trampoline_32bit_src) /* Set up data and stack segments */ @@ -600,6 +603,16 @@ ENTRY(trampoline_32bit_src) leal TRAMPOLINE_32BIT_PGTABLE_OFFSET(%ecx), %eax movl %eax, %cr3 3: + /* Set EFER.LME=1 as a precaution in case hypervsior pulls the rug */ + pushl %ecx + pushl %edx + movl $MSR_EFER, %ecx + rdmsr + btsl $_EFER_LME, %eax + wrmsr + popl %edx + popl %ecx + /* Enable PAE and LA57 (if required) paging modes */ movl $X86_CR4_PAE, %eax cmpl $0, %edx @@ -645,8 +658,6 @@ no_longmode: .data gdt64: .word gdt_end - gdt - .long 0 - .word 0 .quad 0 gdt: .word gdt_end - gdt |