mm, x86/mm: Make the batched unmap TLB flush API more generic
try_to_unmap_flush() used to open-code a rather x86-centric flush
sequence: local_flush_tlb() + flush_tlb_others(). Rearrange the
code so that the arch (only x86 for now) provides
arch_tlbbatch_add_mm() and arch_tlbbatch_flush() and the core code
calls those functions instead.
I'll want this for x86 because, to enable address space ids, I can't
support the flush_tlb_others() mode used by exising
try_to_unmap_flush() implementation with good performance. I can
support the new API fairly easily, though.
I imagine that other architectures may be in a similar position.
Architectures with strong remote flush primitives (arm64?) may have
even worse performance problems with flush_tlb_others() the way that
try_to_unmap_flush() uses it.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/19f25a8581f9fb77876b7ff3b001f89835e34ea3.1495492063.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/include/asm/tlbbatch.h b/arch/x86/include/asm/tlbbatch.h
new file mode 100644
index 0000000..01a6de1
--- /dev/null
+++ b/arch/x86/include/asm/tlbbatch.h
@@ -0,0 +1,16 @@
+#ifndef _ARCH_X86_TLBBATCH_H
+#define _ARCH_X86_TLBBATCH_H
+
+#include <linux/cpumask.h>
+
+#ifdef CONFIG_SMP
+struct arch_tlbflush_unmap_batch {
+ /*
+ * Each bit set is a CPU that potentially has a TLB entry for one of
+ * the PFNs being flushed..
+ */
+ struct cpumask cpumask;
+};
+#endif
+
+#endif /* _ARCH_X86_TLBBATCH_H */
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index b9db0f8fe..8f6e2f8 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -329,6 +329,14 @@ static inline void reset_lazy_tlbstate(void)
this_cpu_write(cpu_tlbstate.active_mm, &init_mm);
}
+static inline void arch_tlbbatch_add_mm(struct arch_tlbflush_unmap_batch *batch,
+ struct mm_struct *mm)
+{
+ cpumask_or(&batch->cpumask, &batch->cpumask, mm_cpumask(mm));
+}
+
+extern void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch);
+
#endif /* SMP */
#ifndef CONFIG_PARAVIRT
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 4d30386..743e4c6 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -395,6 +395,23 @@ void flush_tlb_kernel_range(unsigned long start, unsigned long end)
}
}
+void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
+{
+ int cpu = get_cpu();
+
+ if (cpumask_test_cpu(cpu, &batch->cpumask)) {
+ count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
+ local_flush_tlb();
+ trace_tlb_flush(TLB_LOCAL_SHOOTDOWN, TLB_FLUSH_ALL);
+ }
+
+ if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids)
+ flush_tlb_others(&batch->cpumask, NULL, 0, TLB_FLUSH_ALL);
+ cpumask_clear(&batch->cpumask);
+
+ put_cpu();
+}
+
static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf,
size_t count, loff_t *ppos)
{