Revert "perf/core: Make sure the ring-buffer is mapped in all page-tables"

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>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: David H. Gutteridge <dhgutteridge@sympatico.ca>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <llong@redhat.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: joro@8bytes.org
Link: https://lkml.kernel.org/r/1532533683-5988-3-git-send-email-joro@8bytes.org

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) {