Commit-ID: cdbaf0a372db2bc3c3127e8b63fd15bd6e6757ee
Gitweb: https://git.kernel.org/tip/cdbaf0a372db2bc3c3127e8b63fd15bd6e6757ee
Author: Joerg Roedel <jroe...@suse.de>
AuthorDate: Fri, 20 Jul 2018 18:22:22 +0200
Committer: Thomas Gleixner <t...@linutronix.de>
CommitDate: Fri, 20 Jul 2018 21:32:08 +0200
perf/core: Make sure the ring-buffer is mapped in all page-tables
The ring-buffer is accessed in the NMI handler, so it's better to avoid
faulting on it. Sync the vmalloc range with all page-tables in system to
make sure everyone has it mapped.
This fixes a WARN_ON_ONCE() that can be triggered with PTI enabled on
x86-32:
WARNING: CPU: 4 PID: 0 at arch/x86/mm/fault.c:320 vmalloc_fault+0x220/0x230
This triggers because with PTI enabled on an PAE kernel the PMDs are no
longer shared between the page-tables, so the vmalloc changes do not
propagate automatically.
Note: Andy said rightfully that we should try to fix the vmalloc code for
that case, but that's not a hot fix for the issue at hand.
Fixes: 7757d607c6b3 ("x86/pti: Allow CONFIG_PAGE_TABLE_ISOLATION for x86_32")
Signed-off-by: Joerg Roedel <jroe...@suse.de>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Cc: "H . Peter Anvin" <h...@zytor.com>
Cc: linux...@kvack.org
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Dave Hansen <dave.han...@intel.com>
Cc: Josh Poimboeuf <jpoim...@redhat.com>
Cc: Juergen Gross <jgr...@suse.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Jiri Kosina <jkos...@suse.cz>
Cc: Boris Ostrovsky <boris.ostrov...@oracle.com>
Cc: Brian Gerst <brge...@gmail.com>
Cc: David Laight <david.lai...@aculab.com>
Cc: Denys Vlasenko <dvlas...@redhat.com>
Cc: Eduardo Valentin <edu...@amazon.com>
Cc: Greg KH <gre...@linuxfoundation.org>
Cc: Will Deacon <will.dea...@arm.com>
Cc: aligu...@amazon.com
Cc: daniel.gr...@iaik.tugraz.at
Cc: hu...@google.com
Cc: keesc...@google.com
Cc: Andrea Arcangeli <aarca...@redhat.com>
Cc: Waiman Long <ll...@redhat.com>
Cc: Pavel Machek <pa...@ucw.cz>
Cc: "David H . Gutteridge" <dhgutteri...@sympatico.ca>
Cc: Arnaldo Carvalho de Melo <a...@kernel.org>
Cc: Alexander Shishkin <alexander.shish...@linux.intel.com>
Cc: Jiri Olsa <jo...@redhat.com>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: j...@8bytes.org
Link:
https://lkml.kernel.org/r/1532103744-31902-2-git-send-email-j...@8bytes.org
---
kernel/events/ring_buffer.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 5d3cf407e374..7b0e9aafafdf 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -814,6 +814,9 @@ static void rb_free_work(struct work_struct *work)
vfree(base);
kfree(rb);
+
+ /* Make sure buffer is unmapped in all page-tables */
+ vmalloc_sync_all();
}
void rb_free(struct ring_buffer *rb)
@@ -840,6 +843,13 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark,
int cpu, int flags)
if (!all_buf)
goto fail_all_buf;
+ /*
+ * 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.
+ */
+ vmalloc_sync_all();
+
rb->user_page = all_buf;
rb->data_pages[0] = all_buf + PAGE_SIZE;
if (nr_pages) {
