diff options
authorThomas Gleixner <tglx@linutronix.de>2017-12-30 22:13:54 +0100
committerIngo Molnar <mingo@kernel.org>2017-12-31 12:12:51 +0100
commitdecab0888e6e14e11d53cefa85f8b3d3b45ce73c (patch)
parent322f8b8b340c824aef891342b0f5795d15e11562 (diff)
x86/mm: Remove preempt_disable/enable() from __native_flush_tlb()
The preempt_disable/enable() pair in __native_flush_tlb() was added in commit: 5cf0791da5c1 ("x86/mm: Disable preemption during CR3 read+write") ... to protect the UP variant of flush_tlb_mm_range(). That preempt_disable/enable() pair should have been added to the UP variant of flush_tlb_mm_range() instead. The UP variant was removed with commit: ce4a4e565f52 ("x86/mm: Remove the UP asm/tlbflush.h code, always use the (formerly) SMP code") ... but the preempt_disable/enable() pair stayed around. The latest change to __native_flush_tlb() in commit: 6fd166aae78c ("x86/mm: Use/Fix PCID to optimize user/kernel switches") ... added an access to a per CPU variable outside the preempt disabled regions, which makes no sense at all. __native_flush_tlb() must always be called with at least preemption disabled. Remove the preempt_disable/enable() pair and add a WARN_ON_ONCE() to catch bad callers independent of the smp_processor_id() debugging. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: <stable@vger.kernel.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Linus Torvalds <torvalds@linuxfoundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20171230211829.679325424@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
1 files changed, 8 insertions, 6 deletions
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index b519da4fc03c..f9b48ce152eb 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -345,15 +345,17 @@ static inline void invalidate_user_asid(u16 asid)
static inline void __native_flush_tlb(void)
- invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
- * If current->mm == NULL then we borrow a mm which may change
- * during a task switch and therefore we must not be preempted
- * while we write CR3 back:
+ * Preemption or interrupts must be disabled to protect the access
+ * to the per CPU variable and to prevent being preempted between
+ * read_cr3() and write_cr3().
- preempt_disable();
+ WARN_ON_ONCE(preemptible());
+ invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
+ /* If current->mm == NULL then the read_cr3() "borrows" an mm */
- preempt_enable();

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