From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f71.google.com (mail-wm0-f71.google.com [74.125.82.71]) by kanga.kvack.org (Postfix) with ESMTP id CBC396B0033 for ; Mon, 18 Dec 2017 11:12:55 -0500 (EST) Received: by mail-wm0-f71.google.com with SMTP id 194so7619675wmv.9 for ; Mon, 18 Dec 2017 08:12:55 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id u4si8510255wmg.32.2017.12.18.08.12.53 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 18 Dec 2017 08:12:53 -0800 (PST) From: Greg Kroah-Hartman Subject: [PATCH 4.14 037/178] x86/boot/compressed/64: Detect and handle 5-level paging at boot-time Date: Mon, 18 Dec 2017 16:47:53 +0100 Message-Id: <20171218152922.093379611@linuxfoundation.org> In-Reply-To: <20171218152920.567991776@linuxfoundation.org> References: <20171218152920.567991776@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Kirill A. Shutemov" , Thomas Gleixner , Andi Kleen , Andy Lutomirski , linux-mm@kvack.org, Cyrill Gorcunov , Borislav Petkov , Linus Torvalds 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kirill A. Shutemov commit 08529078d8d9adf689bf39cc38d53979a0869970 upstream. Prerequisite for fixing the current problem of instantaneous reboots when a 5-level paging kernel is booted on 4-level paging hardware. At the same time this change prepares the decompression code to boot-time switching between 4- and 5-level paging. [ tglx: Folded the GCC < 5 fix. ] Fixes: 77ef56e4f0fb ("x86: Enable 5-level paging support via CONFIG_X86_5LEVEL=y") Signed-off-by: Kirill A. Shutemov Signed-off-by: Thomas Gleixner Cc: Andi Kleen Cc: Andy Lutomirski Cc: linux-mm@kvack.org Cc: Cyrill Gorcunov Cc: Borislav Petkov Cc: Linus Torvalds Link: https://lkml.kernel.org/r/20171204124059.63515-2-kirill.shutemov@linux.intel.com Signed-off-by: Greg Kroah-Hartman --- arch/x86/boot/compressed/Makefile | 1 + arch/x86/boot/compressed/head_64.S | 16 ++++++++++++---- arch/x86/boot/compressed/pgtable_64.c | 28 ++++++++++++++++++++++++++++ 3 files changed, 41 insertions(+), 4 deletions(-) --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -78,6 +78,7 @@ vmlinux-objs-$(CONFIG_EARLY_PRINTK) += $ vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr.o ifdef CONFIG_X86_64 vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/pagetable.o + vmlinux-objs-y += $(obj)/pgtable_64.o endif $(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -289,10 +289,18 @@ ENTRY(startup_64) leaq boot_stack_end(%rbx), %rsp #ifdef CONFIG_X86_5LEVEL - /* Check if 5-level paging has already enabled */ - movq %cr4, %rax - testl $X86_CR4_LA57, %eax - jnz lvl5 + /* + * Check if we need to enable 5-level paging. + * RSI holds real mode data and need to be preserved across + * a function call. + */ + pushq %rsi + call l5_paging_required + popq %rsi + + /* If l5_paging_required() returned zero, we're done here. */ + cmpq $0, %rax + je lvl5 /* * At this point we are in long mode with 4-level paging enabled, --- /dev/null +++ b/arch/x86/boot/compressed/pgtable_64.c @@ -0,0 +1,28 @@ +#include + +/* + * __force_order is used by special_insns.h asm code to force instruction + * serialization. + * + * It is not referenced from the code, but GCC < 5 with -fPIE would fail + * due to an undefined symbol. Define it to make these ancient GCCs work. + */ +unsigned long __force_order; + +int l5_paging_required(void) +{ + /* Check if leaf 7 is supported. */ + + if (native_cpuid_eax(0) < 7) + return 0; + + /* Check if la57 is supported. */ + if (!(native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31)))) + return 0; + + /* Check if 5-level paging has already been enabled. */ + if (native_read_cr4() & X86_CR4_LA57) + return 0; + + return 1; +} -- 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