diff options
| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2018-05-18 13:35:25 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-05-19 11:56:57 +0200 |
| commit | 372fddf709041743a93e381556f4c41aad1e28f8 (patch) | |
| tree | 318f2d073ebfdd56e25f726d2675c4dd09544986 /arch/x86/boot | |
| parent | ed7588d5dc6f5e7202fb9bbeb14d94706ba225d7 (diff) | |
x86/mm: Introduce the 'no5lvl' kernel parameter
This kernel parameter allows to force kernel to use 4-level paging even
if hardware and kernel support 5-level paging.
The option may be useful to work around regressions related to 5-level
paging.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180518103528.59260-5-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/boot')
| -rw-r--r-- | arch/x86/boot/compressed/cmdline.c | 2 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/head_64.S | 1 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/pgtable_64.c | 12 |
3 files changed, 12 insertions, 3 deletions
diff --git a/arch/x86/boot/compressed/cmdline.c b/arch/x86/boot/compressed/cmdline.c index 0cb325734cfb..af6cda0b7900 100644 --- a/arch/x86/boot/compressed/cmdline.c +++ b/arch/x86/boot/compressed/cmdline.c @@ -1,7 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 #include "misc.h" -#if CONFIG_EARLY_PRINTK || CONFIG_RANDOMIZE_BASE +#if CONFIG_EARLY_PRINTK || CONFIG_RANDOMIZE_BASE || CONFIG_X86_5LEVEL static unsigned long fs; static inline void set_fs(unsigned long seg) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 8169e8b7a4dc..64037895b085 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -365,6 +365,7 @@ ENTRY(startup_64) * this function call. */ pushq %rsi + movq %rsi, %rdi /* real mode address */ call paging_prepare popq %rsi diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c index 23707e1da1ff..8c5107545251 100644 --- a/arch/x86/boot/compressed/pgtable_64.c +++ b/arch/x86/boot/compressed/pgtable_64.c @@ -31,16 +31,23 @@ static char trampoline_save[TRAMPOLINE_32BIT_SIZE]; */ unsigned long *trampoline_32bit __section(.data); -struct paging_config paging_prepare(void) +extern struct boot_params *boot_params; +int cmdline_find_option_bool(const char *option); + +struct paging_config paging_prepare(void *rmode) { struct paging_config paging_config = {}; unsigned long bios_start, ebda_start; + /* Initialize boot_params. Required for cmdline_find_option_bool(). */ + boot_params = rmode; + /* * Check if LA57 is desired and supported. * - * There are two parts to the check: + * There are several parts to the check: * - if the kernel supports 5-level paging: CONFIG_X86_5LEVEL=y + * - if user asked to disable 5-level paging: no5lvl in cmdline * - if the machine supports 5-level paging: * + CPUID leaf 7 is supported * + the leaf has the feature bit set @@ -48,6 +55,7 @@ struct paging_config paging_prepare(void) * That's substitute for boot_cpu_has() in early boot code. */ if (IS_ENABLED(CONFIG_X86_5LEVEL) && + !cmdline_find_option_bool("no5lvl") && native_cpuid_eax(0) >= 7 && (native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31)))) { paging_config.l5_required = 1; |