From 77754cfa09a6c528c38cbca9ee4cc4f7cf6ad6f2 Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Fri, 20 Jul 2018 18:22:22 +0200 Subject: [PATCH] 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 Signed-off-by: Thomas Gleixner Cc: "H . Peter Anvin" Cc: linux-mm@kvack.org Cc: Linus Torvalds Cc: Andy Lutomirski Cc: Dave Hansen Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Jiri Kosina Cc: Boris Ostrovsky Cc: Brian Gerst Cc: David Laight Cc: Denys Vlasenko Cc: Eduardo Valentin Cc: Greg KH Cc: Will Deacon Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Cc: Andrea Arcangeli Cc: Waiman Long Cc: Pavel Machek Cc: "David H . Gutteridge" Cc: Arnaldo Carvalho de Melo Cc: Alexander Shishkin Cc: Jiri Olsa Cc: Namhyung Kim Cc: joro@8bytes.org Link: https://lkml.kernel.org/r/1532103744-31902-2-git-send-email-joro@8bytes.org --- kernel/events/ring_buffer.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 5d3cf407e374..df2d8cf0072c 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -814,6 +814,13 @@ 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) @@ -840,6 +847,15 @@ 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) { -- 2.30.2