diff options
| author | Steven Rostedt <srostedt@redhat.com> | 2012-02-24 20:55:13 (GMT) |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2012-02-24 20:55:13 (GMT) |
| commit | 79fb4ad63e8266ffac1f69bbb45a6f86570493e7 (patch) | |
| tree | a093b0a3b175b8cad72682b3d37a3dc8002e9fbd /arch/x86/kernel/entry_64.S | |
| parent | 626109130267713cac020515504ec341e47c96f9 (diff) | |
| download | linux-79fb4ad63e8266ffac1f69bbb45a6f86570493e7.tar.xz | |
x86: Fix the NMI nesting comments
Some of the comments for the nesting NMI algorithm were stale and
had some references to some prototypes that were first tried.
I also updated the comments to be a little easier to understand
the flow of the code. It definitely needs the documentation.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'arch/x86/kernel/entry_64.S')
| -rw-r--r-- | arch/x86/kernel/entry_64.S | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index e0eca00..2de3e45 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 |