From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id 5A28C6B039F for ; Tue, 18 Jul 2017 10:15:39 -0400 (EDT) Received: by mail-pg0-f69.google.com with SMTP id t8so22825694pgs.5 for ; Tue, 18 Jul 2017 07:15:39 -0700 (PDT) Received: from mga01.intel.com (mga01.intel.com. [192.55.52.88]) by mx.google.com with ESMTPS id w15si1912933plk.57.2017.07.18.07.15.38 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Jul 2017 07:15:38 -0700 (PDT) From: "Kirill A. Shutemov" Subject: [PATCHv2 03/10] x86/boot/compressed/64: Detect and handle 5-level paging at boot-time Date: Tue, 18 Jul 2017 17:15:10 +0300 Message-Id: <20170718141517.52202-4-kirill.shutemov@linux.intel.com> In-Reply-To: <20170718141517.52202-1-kirill.shutemov@linux.intel.com> References: <20170718141517.52202-1-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds , Andrew Morton , x86@kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" Cc: Andi Kleen , Dave Hansen , Andy Lutomirski , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" This patch prepare decompression code to boot-time switching between 4- and 5-level paging. Signed-off-by: Kirill A. Shutemov --- 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 fbf4c32d0b62..2e362aea3319 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -347,6 +347,28 @@ preferred_addr: leaq boot_stack_end(%rbx), %rsp #ifdef CONFIG_X86_5LEVEL + /* Preserve rbx across cpuid */ + movq %rbx, %r8 + + /* Check if leaf 7 is supported */ + movl $0, %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 + movl $0, %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 @@ -386,6 +408,8 @@ preferred_addr: pushq %rax lretq lvl5: + /* Restore rbx */ + movq %r8, %rbx #endif /* Zero EFLAGS */ -- 2.11.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org