Commit-ID: 79fb4ad63e8266ffac1f69bbb45a6f86570493e7 Gitweb: http://git.kernel.org/tip/79fb4ad63e8266ffac1f69bbb45a6f86570493e7 Author: Steven Rostedt <srostedt@xxxxxxxxxx> AuthorDate: Fri, 24 Feb 2012 15:55:13 -0500 Committer: Steven Rostedt <rostedt@xxxxxxxxxxx> CommitDate: Fri, 24 Feb 2012 15:55:13 -0500 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@xxxxxxxxxxx> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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