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Date: Wed, 1 Nov 2017 14:55:01 +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: Andy Lutomirski <luto@...capital.net>, Cyrill Gorcunov <gorcunov@...nvz.org>, Borislav Petkov <bp@...e.de>, Andi Kleen <ak@...ux.intel.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> Subject: [PATCH 2/4] 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 | 16 ++++++++++++---- arch/x86/boot/compressed/pagetable.c | 19 +++++++++++++++++++ 2 files changed, 31 insertions(+), 4 deletions(-) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index b4a5d284391c..6ac8239af2b6 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -288,10 +288,18 @@ 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 need_to_enabled_l5 + popq %rsi + + /* If need_to_enabled_l5() returned zero, we're done here. */ + cmpq $0, %rax + je lvl5 /* * At this point we are in long mode with 4-level paging enabled, diff --git a/arch/x86/boot/compressed/pagetable.c b/arch/x86/boot/compressed/pagetable.c index a15bbfcb3413..cd2dd49333cc 100644 --- a/arch/x86/boot/compressed/pagetable.c +++ b/arch/x86/boot/compressed/pagetable.c @@ -154,3 +154,22 @@ void finalize_identity_maps(void) } #endif /* CONFIG_RANDOMIZE_BASE */ + +#ifdef CONFIG_X86_5LEVEL +int need_to_enabled_l5(void) +{ + /* Check i 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; +} +#endif -- 2.14.2
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