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Date: Mon, 18 Sep 2017 13:55:40 +0300 From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> To: Ingo Molnar <mingo@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Andy Lutomirski <luto@...capital.net>, Cyrill Gorcunov <gorcunov@...nvz.org>, Borislav Petkov <bp@...e.de>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> Subject: [PATCHv7 06/19] x86/boot/compressed/64: Detect and handle 5-level paging at boot-time This patch prepare decompression code to boot-time switching between 4- and 5-level paging. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> --- 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 */ + movq %r8, %rbx + /* Check if 5-level paging has already enabled */ movq %cr4, %rax testl $X86_CR4_LA57, %eax @@ -327,6 +349,8 @@ ENTRY(startup_64) pushq %rax lretq lvl5: + /* Restore rbx */ + movq %r8, %rbx #endif /* Zero EFLAGS */ -- 2.14.1
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