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| author | Andy Lutomirski <luto@amacapital.net> | 2014-10-25 00:58:08 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-02-04 12:10:42 +0100 |
| commit | 1e02ce4cccdcb9688386e5b8d2c9fa4660b45389 (patch) | |
| tree | 7d514286844acea505228590119ac1a886cf6995 /arch/x86/kernel/setup.c | |
| parent | x86: Clean up cr4 manipulation (diff) | |
| download | linux-1e02ce4cccdcb9688386e5b8d2c9fa4660b45389.tar.xz linux-1e02ce4cccdcb9688386e5b8d2c9fa4660b45389.zip | |
x86: Store a per-cpu shadow copy of CR4
Context switches and TLB flushes can change individual bits of CR4.
CR4 reads take several cycles, so store a shadow copy of CR4 in a
per-cpu variable.
To avoid wasting a cache line, I added the CR4 shadow to
cpu_tlbstate, which is already touched in switch_mm. The heaviest
users of the cr4 shadow will be switch_mm and __switch_to_xtra, and
__switch_to_xtra is called shortly after switch_mm during context
switch, so the cacheline is likely to be hot.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Vince Weaver <vince@deater.net>
Cc: "hillf.zj" <hillf.zj@alibaba-inc.com>
Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/3a54dd3353fffbf84804398e00dfdc5b7c1afd7d.1414190806.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/setup.c')
| -rw-r--r-- | arch/x86/kernel/setup.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index ab4734e5411d..04e6c62f1a93 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1178,7 +1178,7 @@ void __init setup_arch(char **cmdline_p) if (boot_cpu_data.cpuid_level >= 0) { /* A CPU has %cr4 if and only if it has CPUID */ - mmu_cr4_features = read_cr4(); + mmu_cr4_features = __read_cr4(); if (trampoline_cr4_features) *trampoline_cr4_features = mmu_cr4_features; } |