* Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> wrote: > This patch prepare decompression code to boot-time switching between 4- > and 5-level paging. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > --- > arch/x86/boot/compressed/head_64.S | 24 ++++++++++++++++++++++++ > 1 file changed, 24 insertions(+) > > diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S > index b4a5d284391c..09c85e8558eb 100644 > --- a/arch/x86/boot/compressed/head_64.S > +++ b/arch/x86/boot/compressed/head_64.S > @@ -288,6 +288,28 @@ ENTRY(startup_64) > leaq boot_stack_end(%rbx), %rsp > > #ifdef CONFIG_X86_5LEVEL > + /* Preserve rbx across cpuid */ > + movq %rbx, %r8 > + > + /* Check if leaf 7 is supported */ > + xorl %eax, %eax > + cpuid > + cmpl $7, %eax > + jb lvl5 > + > + /* > + * Check if la57 is supported. > + * The feature is enumerated with CPUID.(EAX=07H, ECX=0):ECX[bit 16] > + */ > + movl $7, %eax > + xorl %ecx, %ecx > + cpuid > + andl $(1 << 16), %ecx > + jz lvl5 > + > + /* Restore rbx */ In (new) x86 asm code we refer to registers in capital letters. Also, CPUID should be capitalized consistently as well. Also, LA57 should be capitalized as well. > + movq %r8, %rbx > + > /* Check if 5-level paging has already enabled */ > movq %cr4, %rax BTW., please also fix the typo in this comment while at it. Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
