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

[Joerg Roedel <joro@8bytes.org>]

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