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SubjectRe: [PATCH v3 2/7] x86/jump_label: Use text_poke_early() during early_init
On Fri, Nov 02, 2018 at 04:29:41PM -0700, Nadav Amit wrote:
> diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
> index aac0c1f7e354..367c1d0c20a3 100644
> --- a/arch/x86/kernel/jump_label.c
> +++ b/arch/x86/kernel/jump_label.c
> @@ -52,7 +52,13 @@ static void __ref __jump_label_transform(struct jump_entry *entry,
> jmp.offset = jump_entry_target(entry) -
> (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
>
> - if (early_boot_irqs_disabled)
> + /*
> + * As long as we are in early boot, we can use text_poke_early(), which
> + * is more efficient: the memory was still not marked as read-only (it
> + * is only marked after poking_init()). This also prevents us from using
> + * text_poke() before poking_init() is called.
> + */
> + if (!early_boot_done)
> poker = text_poke_early;
>
> if (type == JUMP_LABEL_JMP) {

It took me a while to untangle init/maze^H^Hin.c... but I think this
is all we need:

diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index aac0c1f7e354..ed5fe274a7d8 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -52,7 +52,12 @@ static void __ref __jump_label_transform(struct jump_entry *entry,
jmp.offset = jump_entry_target(entry) -
(jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);

- if (early_boot_irqs_disabled)
+ /*
+ * As long as we're UP and not yet marked RO, we can use
+ * text_poke_early; SYSTEM_BOOTING guarantees both, as we switch to
+ * SYSTEM_SCHEDULING before going either.
+ */
+ if (system_state == SYSTEM_BOOTING)
poker = text_poke_early;

if (type == JUMP_LABEL_JMP) {
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