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| 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/kernel/head64.c | |
| parent | ed7588d5dc6f5e7202fb9bbeb14d94706ba225d7 (diff) | |
| download | lwn-372fddf709041743a93e381556f4c41aad1e28f8.tar.gz lwn-372fddf709041743a93e381556f4c41aad1e28f8.zip | |
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/kernel/head64.c')
| -rw-r--r-- | arch/x86/kernel/head64.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 8d372d1c266d..8047379e575a 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -80,10 +80,11 @@ static unsigned int __head *fixup_int(void *ptr, unsigned long physaddr) static bool __head check_la57_support(unsigned long physaddr) { - if (native_cpuid_eax(0) < 7) - return false; - - if (!(native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31)))) + /* + * 5-level paging is detected and enabled at kernel decomression + * stage. Only check if it has been enabled there. + */ + if (!(native_read_cr4() & X86_CR4_LA57)) return false; *fixup_int(&__pgtable_l5_enabled, physaddr) = 1; |