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x86/mm: Allow to boot without LA57 if CONFIG_X86_5LEVEL=y

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All pieces of the puzzle are in place and we can now allow to boot with
CONFIG_X86_5LEVEL=y on a machine without LA57 support.

Kernel will detect that LA57 is missing and fold p4d at runtime.

Update the documentation and the Kconfig option description to reflect the
change.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180214182542.69302-10-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Kirill A. Shutemov 2018-02-14 21:25:42 +03:00 committed by Ingo Molnar
parent 91f606a8fa
commit 6657fca06e
4 changed files with 6 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
Documentation/x86/x86_64/5level-paging.txt
View File

@ -20,12 +20,9 @@ Documentation/x86/x86_64/mm.txt
CONFIG_X86_5LEVEL=y enables the feature.
So far, a kernel compiled with the option enabled will be able to boot
only on machines that supports the feature -- see for 'la57' flag in
/proc/cpuinfo.
The plan is to implement boot-time switching between 4- and 5-level paging
in the future.
Kernel with CONFIG_X86_5LEVEL=y still able to boot on 4-level hardware.
In this case additional page table level -- p4d -- will be folded at
runtime.
== User-space and large virtual address space ==

4
arch/x86/Kconfig
View File

@ -1440,8 +1440,8 @@ config X86_5LEVEL
It will be supported by future Intel CPUs.
Note: a kernel with this option enabled can only be booted
on machines that support the feature.
A kernel with the option enabled can be booted on machines that
support 4- or 5-level paging.
See Documentation/x86/x86_64/5level-paging.txt for more
information.

16
arch/x86/boot/compressed/misc.c
View File

@ -169,16 +169,6 @@ void __puthex(unsigned long value)
}
}
static bool l5_supported(void)
{
/* Check if leaf 7 is supported. */
if (native_cpuid_eax(0) < 7)
return 0;
/* Check if la57 is supported. */
return native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31));
}
#if CONFIG_X86_NEED_RELOCS
static void handle_relocations(void *output, unsigned long output_len,
unsigned long virt_addr)
@ -372,12 +362,6 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
console_init();
debug_putstr("early console in extract_kernel\n");
if (IS_ENABLED(CONFIG_X86_5LEVEL) && !l5_supported()) {
error("This linux kernel as configured requires 5-level paging\n"
"This CPU does not support the required 'cr4.la57' feature\n"
"Unable to boot - please use a kernel appropriate for your CPU\n");
}
free_mem_ptr = heap; /* Heap */
free_mem_end_ptr = heap + BOOT_HEAP_SIZE;

8
arch/x86/include/asm/required-features.h
View File

@ -53,12 +53,6 @@
# define NEED_MOVBE 0
#endif
#ifdef CONFIG_X86_5LEVEL
# define NEED_LA57 (1<<(X86_FEATURE_LA57 & 31))
#else
# define NEED_LA57 0
#endif
#ifdef CONFIG_X86_64
#ifdef CONFIG_PARAVIRT
/* Paravirtualized systems may not have PSE or PGE available */
@ -104,7 +98,7 @@
#define REQUIRED_MASK13 0
#define REQUIRED_MASK14 0
#define REQUIRED_MASK15 0
#define REQUIRED_MASK16 (NEED_LA57)
#define REQUIRED_MASK16 0
#define REQUIRED_MASK17 0
#define REQUIRED_MASK18 0
#define REQUIRED_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != 19)