Messages in this thread Patch in this message | | | Date | Fri, 20 Jul 2018 12:37:07 -0700 | From | tip-bot for Joerg Roedel <> | Subject | [tip:x86/pti] perf/core: Make sure the ring-buffer is mapped in all page-tables |
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Commit-ID: cdbaf0a372db2bc3c3127e8b63fd15bd6e6757ee Gitweb: https://git.kernel.org/tip/cdbaf0a372db2bc3c3127e8b63fd15bd6e6757ee Author: Joerg Roedel <jroedel@suse.de> AuthorDate: Fri, 20 Jul 2018 18:22:22 +0200 Committer: Thomas Gleixner <tglx@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 <jroedel@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> 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: "David H . Gutteridge" <dhgutteridge@sympatico.ca> 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/1532103744-31902-2-git-send-email-joro@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) {
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