From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752168AbdHGOQI (ORCPT ); Mon, 7 Aug 2017 10:16:08 -0400 Received: from mga07.intel.com ([134.134.136.100]:24194 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750751AbdHGOQH (ORCPT ); Mon, 7 Aug 2017 10:16:07 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,338,1498546800"; d="scan'208";a="887441056" From: "Kirill A. Shutemov" 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" Subject: [PATCHv3 05/13] x86/boot/compressed/64: Detect and handle 5-level paging at boot-time Date: Mon, 7 Aug 2017 17:14:43 +0300 Message-Id: <20170807141451.80934-6-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.13.2 In-Reply-To: <20170807141451.80934-1-kirill.shutemov@linux.intel.com> References: <20170807141451.80934-1-kirill.shutemov@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 */ -- 2.13.2