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

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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
This commit is contained in:
Joerg Roedel 2018-07-20 18:22:22 +02:00 committed by Thomas Gleixner
parent 8c934e01a7
commit 77754cfa09
1 changed files with 16 additions and 0 deletions
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16
kernel/events/ring_buffer.c
View File

@ -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) {