Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull perf fixes from Ingo Molnar:

 - an s2ram related fix on AMD systems

 - a perf fault handling bug that is relatively old but which has become
   much easier to trigger in v3.13 after commit e00b12e64be9 ("perf/x86:
   Further optimize copy_from_user_nmi()")

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/amd/ibs: Fix waking up from S3 for AMD family 10h
  x86, mm, perf: Allow recursive faults from interrupts

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 9ff85bb8dd69..9d591c895803 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -641,6 +641,20 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 
         /* Are we prepared to handle this kernel fault? */
         if (fixup_exception(regs)) {
+                /*
+                 * Any interrupt that takes a fault gets the fixup. This makes
+                 * the below recursive fault logic only apply to a faults from
+                 * task context.
+                 */
+                if (in_interrupt())
+                        return;
+
+                /*
+                 * Per the above we're !in_interrupt(), aka. task context.
+                 *
+                 * In this case we need to make sure we're not recursively
+                 * faulting through the emulate_vsyscall() logic.
+                 */
                 if (current_thread_info()->sig_on_uaccess_error && signal) {
                         tsk->thread.trap_nr = X86_TRAP_PF;
                         tsk->thread.error_code = error_code | PF_USER;
@@ -649,6 +663,10 @@ no_context(struct pt_regs *regs, unsigned long error_code,
                         /* XXX: hwpoison faults will set the wrong code. */
                         force_sig_info_fault(signal, si_code, address, tsk, 0);
                 }
+
+                /*
+                 * Barring that, we can do the fixup and be happy.
+                 */
                 return;
         }