Hi Masami,
On Wed, Mar 25, 2026 at 11:22:04PM +0900, Masami Hiramatsu wrote:
On Wed, 25 Mar 2026 03:05:38 -0700
Breno Leitao [off-list ref] wrote:
quoted
+/*
+ * bootconfig_apply_early_params - dispatch kernel.* keys from the embedded
+ * bootconfig as early_param() calls.
+ *
+ * early_param() handlers must run before most of the kernel initialises
+ * (e.g. before the GIC driver reads irqchip.gicv3_pseudo_nmi). A bootconfig
+ * attached to the initrd arrives too late for this because the initrd is not
+ * mapped yet when early params are processed. The embedded bootconfig lives
+ * in the kernel image itself (.init.data), so it is always reachable.
+ *
+ * This function is called from setup_boot_config() which runs in
+ * start_kernel() before parse_early_param(), making the timing correct.
+ */
+static void __init bootconfig_apply_early_params(void)
[sashiko comment]
| Does this run early enough for architectural parameters?
| While setup_boot_config() runs before parse_early_param() in start_kernel(),
| it runs after setup_arch(). setup_boot_config() relies on xbc_init() which
| uses the memblock allocator, requiring setup_arch() to have already
| initialized it.
| However, the kernel expects many early parameters (like mem=, earlycon,
| noapic, and iommu) to be parsed during setup_arch() via the architecture's
| call to parse_early_param(). Since setup_arch() completes before
| setup_boot_config() runs, will these architectural early parameters be
| silently ignored because the decisions they influence were already
| finalized?
This is the major reason that I did not support early parameter
in bootconfig. Some archs initialize kernel_cmdline in setup_arch()
and setup early parameters in it.
Would it be feasible to document which parameters are architecture-specific
and must be processed during setup_arch()?
We could potentially introduce a third parameter category alongside the
existing early_param() and __setup():
* early_param()
* __setup()
* early_arch_param() (New)
This would allow bootconfig to support __setup() and early_param() while
explicitly excluding early_arch_param() from bootconfig processing.
This would move break down the early parameters in those that can be
easily handled.
To fix this, we need to change setup_arch() for each architecture so
that it calls this bootconfig_apply_early_params().
Could we instead integrate this into parse_early_param() itself? That
approach would avoid the need to modify each architecture individually.
Thanks for looking at it,
--breno