Re: [PATCH v25 03/10] firmware: psci: Introduce command-based resets

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The restart handler `psci_sys_reset()` unintentionally skips configured reset commands for standard reboots due to checking if `data` is non-NULL.
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commit 15791809d0deec27e24e64483b3317dacb5842a5
Author: Shivendra Pratap <shivendra.pratap@oss.qualcomm.com>

firmware: psci: Introduce command-based resets

This commit introduces a command-based reset mechanism allowing reboot-mode
drivers to specify custom PSCI reset commands like vendor-specific
SYSTEM_RESET2. It defaults to the existing reboot_mode flow unless a valid
reset command is configured.

> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index e73bae6cb23a3..d489ba5d147ce 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c

[ ... ]

> @@ -320,6 +409,30 @@ static int psci_sys_reset(struct notifier_block *nb, unsigned long action,

[ ... ]

> +static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
> +			  void *data)
> +{
> +	const struct psci_system_reset_cmd *cmd;
> +
> +	/* The function psci_handle_reboot_mode follows reboot_mode based
> +	 * reset flow and psci_handle_reset_cmd uses reset_cmd based reset flow.
> +	 *
> +	 * The reset_cmd is configured at the reboot_notifier phase.
> +	 * If panic() or emergency_restart() occurs between the reboot_notifier
> +	 * and this final reset, skip command-based reset and let reboot_mode drive
> +	 * the reset flow.
> +	 *
> +	 * The function psci_handle_reset_cmd invokes non-returning PSCI SYSTEM_RESET
> +	 * calls to reset the device. If it returns, either the reset failed, or the
> +	 * command was unsupported. Fallback to reboot_mode based reset flow.
> +	 */
> +	cmd = smp_load_acquire(&reset_cmd);
> +	if (data && cmd && !panic_in_progress())
> +		psci_handle_reset_cmd(cmd);

[Severity: High]
Will this check unintentionally skip custom reset commands during a standard
reboot?

When a standard userspace reboot is triggered via the reboot syscall with
LINUX_REBOOT_CMD_RESTART, the reboot sequence ultimately calls
kernel_restart(NULL). 

This propagates down to the atomic restart notifier chain in
do_kernel_restart(NULL), which passes a NULL command pointer to the notifier
handlers.

In psci_sys_reset(), the data parameter receives this NULL pointer. Because
of the check for a non-NULL data variable, the condition evaluates to false,
causing the handler to skip psci_handle_reset_cmd(). It then incorrectly
falls back to psci_handle_reboot_mode(), even if a valid command was
successfully configured by a reboot-mode driver.

Is the data check acting contrary to the commit message's goal of ignoring
reset commands during panic and emergency_restart?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260914-arm-psci-system_reset2-vendor-reboots-v25-0-4aaf5c09b5c2@oss.qualcomm.com?part=3