[PATCH 2/3] Revert "perf/core: Make sure the ring-buffer is mapped in all page-tables"

Joerg Roedel
2018-07-25T15:48:33Z

From: Joerg Roedel <jroedel@suse.de>

This reverts commit 77754cfa09a6c528c38cbca9ee4cc4f7cf6ad6f2.

The patch was necessary to silence a WARN_ON_ONCE(in_nmi())
that triggered in the vmalloc_fault() function when PTI was
enabled on x86-32.

Faulting in an NMI handler turned out to be safe and the
warning in vmalloc_fault() is gone now. So the above patch
can be reverted.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
kernel/events/ring_buffer.c | 16 ----------------
1 file changed, 16 deletions(-)

diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index df2d8cf..5d3cf40 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -814,13 +814,6 @@ static void rb_free_work(struct work_struct *work)

vfree(base);
kfree(rb);
-
- /*
- * FIXME: PAE workaround for vmalloc_fault(): Make sure buffer is
- * unmapped in all page-tables.
- */
- if (IS_ENABLED(CONFIG_X86_PAE))
- vmalloc_sync_all();
}

void rb_free(struct ring_buffer *rb)
@@ -847,15 +840,6 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
if (!all_buf)
goto fail_all_buf;

- /*
- * FIXME: PAE workaround for vmalloc_fault(): The buffer is
- * accessed in NMI handlers, make sure it is mapped in all
- * page-tables in the system so that we don't fault on the range in
- * an NMI handler.
- */
- if (IS_ENABLED(CONFIG_X86_PAE))
- vmalloc_sync_all();
-
rb->user_page = all_buf;
rb->data_pages[0] = all_buf + PAGE_SIZE;
if (nr_pages) {
--
2.7.4