1 files changed, 8 insertions, 6 deletions

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index e0eca007dc0d..2de3e457bd4b 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1624,11 +1624,12 @@ first_nmi:
          * | pt_regs                 |
          * +-------------------------+
          *
-         * The saved RIP is used to fix up the copied RIP that a nested
-         * NMI may zero out. The original stack frame and the temp storage
+         * The saved stack frame is used to fix up the copied stack frame
+         * that a nested NMI may change to make the interrupted NMI iret jump
+         * to the repeat_nmi. The original stack frame and the temp storage
          * is also used by nested NMIs and can not be trusted on exit.
          */
-        /* Do not pop rdx, nested NMIs will corrupt it */
+        /* Do not pop rdx, nested NMIs will corrupt that part of the stack */
         movq (%rsp), %rdx
         CFI_RESTORE rdx
 
@@ -1641,6 +1642,8 @@ first_nmi:
         .endr
         CFI_DEF_CFA_OFFSET SS+8-RIP
 
+        /* Everything up to here is safe from nested NMIs */
+
         /*
          * If there was a nested NMI, the first NMI's iret will return
          * here. But NMIs are still enabled and we can take another
@@ -1667,9 +1670,8 @@ end_repeat_nmi:
 
         /*
          * Everything below this point can be preempted by a nested
-         * NMI if the first NMI took an exception. Repeated NMIs
-         * caused by an exception and nested NMI will start here, and
-         * can still be preempted by another NMI.
+         * NMI if the first NMI took an exception and reset our iret stack
+         * so that we repeat another NMI.
          */
         pushq_cfi $-1           /* ORIG_RAX: no syscall to restart */
         subq $ORIG_RAX-R15, %rsp