Re: [PATCH i-g-t 1/2] lib/igt_pm: Add helpers for hibernating kernel

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Tue, Dec 03, 2024 at 11:24:17AM +0200, Juha-Pekka Heikkila wrote:
> Here added
> 
> igt_pm_check_hibernation_support()
> igt_pm_ensure_grub_boots_same_kernel()
> 
> to check if kernel is configured for resuming from hibernation
> and helper to set grub booting currently run kernel on next reboot.
> 
> Signed-off-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> ---
>  lib/igt_pm.c | 155 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  lib/igt_pm.h |   2 +
>  2 files changed, 157 insertions(+)
> 
> diff --git a/lib/igt_pm.c b/lib/igt_pm.c
> index 1a5d9c42b..2055996bc 100644
> --- a/lib/igt_pm.c
> +++ b/lib/igt_pm.c
> @@ -1470,3 +1470,158 @@ void igt_pm_ignore_slpc_efficient_freq(int i915, int gtfd, bool val)
>  	igt_require(igt_sysfs_has_attr(gtfd, "slpc_ignore_eff_freq"));
>  	igt_sysfs_set_u32(gtfd, "slpc_ignore_eff_freq", val);
>  }
> +
> +/**
> + * igt_pm_check_hibernation_support:
> + *
> + * Return: True if kernel is configured with resume point for hibernate.
> + */
> +bool igt_pm_check_hibernation_support(void)
> +{
> +	int fd;
> +	char buffer[2048];
> +	ssize_t bytes_read;
> +	FILE *cmdline;
> +
> +	/* Check if hibernation is supported in /sys/power/state */
> +	fd = open("/sys/power/state", O_RDONLY);
> +
> +	if (fd <= 0) {
> +		igt_debug("Failed to open /sys/power/state\n");
> +		return false;
> +	}
> +
> +	bytes_read = read(fd, buffer, sizeof(buffer) - 1);
> +	close(fd);
> +
> +	if (bytes_read <= 0) {
> +		igt_debug("Failed to read /sys/power/state");
> +		return false;
> +	}
> +
> +	buffer[bytes_read] = '\0';
> +	if (strstr(buffer, "disk") == NULL) {
> +		igt_debug("Hibernation (suspend to disk) is not supported on this system.\n");
> +		return false;
> +	}
> +
> +	/* Check if resume is configured in kernel command line */
> +	cmdline = fopen("/proc/cmdline", "r");
> +
> +	if (!cmdline) {
> +		igt_debug("Failed to open /proc/cmdline");
> +		return false;
> +	}
> +
> +	fread(buffer, 1, sizeof(buffer) - 1, cmdline);
> +	fclose(cmdline);
> +
> +	if (strstr(buffer, "resume=") == NULL) {
> +		igt_debug("Kernel does not have 'resume' parameter configured for hibernation.\n");
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +/**
> + * igt_pm_ensure_grub_boots_same_kernel:
> + *
> + * Return: True if kernel was found and set for next reboot.
> + */
> +bool igt_pm_ensure_grub_boots_same_kernel(void)
> +{
> +	char cmdline[1024];
> +	char current_kernel[256];
> +	char last_menuentry[512] = "";
> +	char grub_entry[512];
> +	char command[1024];
> +	FILE *cmdline_file, *grub_cfg;
> +	char line[1024];
> +	bool kernel_found = false;
> +	char *kernel_arg;
> +	char *kernel_end;
> +
> +	/* Read /proc/cmdline to get the current kernel image */
> +	cmdline_file = fopen("/proc/cmdline", "r");
> +	if (!cmdline_file) {
> +		igt_debug("Failed to open /proc/cmdline");
> +		return false;
> +	}
> +
> +	if (!fgets(cmdline, sizeof(cmdline), cmdline_file)) {
> +		fclose(cmdline_file);
> +		igt_debug("Failed to read /proc/cmdline");
> +		return false;
> +	}
> +	fclose(cmdline_file);
> +
> +	/* Parse the kernel image from cmdline */
> +	kernel_arg = strstr(cmdline, "BOOT_IMAGE=");
> +	if (!kernel_arg) {
> +		igt_debug("BOOT_IMAGE= not found in /proc/cmdline\n");
> +		return false;
> +	}
> +
> +	kernel_arg += strlen("BOOT_IMAGE=");
> +	kernel_end = strchr(kernel_arg, ' ');
> +
> +	if (!kernel_end)
> +		kernel_end = kernel_arg + strlen(kernel_arg);
> +
> +	snprintf(current_kernel, sizeof(current_kernel), "%.*s",
> +		 (int)(kernel_end - kernel_arg), kernel_arg);
> +	igt_debug("Current kernel image: %s\n", current_kernel);
> +
> +	/* Open GRUB config file to find matching entry */
> +	grub_cfg = fopen("/boot/grub/grub.cfg", "r");

The problem is that this depends on distro and with or without EFI...

in my Fedora here:

$ cat /boot/grub/grub.cfg
cat: /boot/grub/grub.cfg: No such file or directory


> +	if (!grub_cfg) {
> +		igt_debug("Failed to open GRUB configuration file");
> +		return false;
> +	}
> +
> +	while (fgets(line, sizeof(line), grub_cfg)) {
> +		/* Check if the line contains a menuentry */
> +		if (strstr(line, "menuentry")) {

Also I believe this can change from distro to distro...
It should be better to have a generic way using other tools that
could give us the default or next boot...

> +		/* Store the menuentry line */
> +			char *start = strchr(line, '\'');
> +			char *end = start ? strchr(start + 1, '\'') : NULL;
> +
> +			if (start && end) {
> +				snprintf(last_menuentry,
> +					 sizeof(last_menuentry),
> +					 "%.*s", (int)(end - start - 1),
> +					 start + 1);
> +			}
> +		}
> +
> +		/* Check if the current line contains the kernel */
> +		if (strstr(line, current_kernel)) {
> +			/* Use the last seen menuentry as the match */
> +			snprintf(grub_entry, sizeof(grub_entry), "%s",
> +				 last_menuentry);
> +			kernel_found = true;
> +			break;
> +		}
> +	}
> +
> +	fclose(grub_cfg);
> +
> +	if (!kernel_found) {
> +		igt_debug("Failed to find matching GRUB entry for kernel: %s\n",
> +			  current_kernel);
> +		return false;
> +	}
> +
> +	/* Set the GRUB boot target using grub-reboot */
> +	snprintf(command, sizeof(command), "grub-reboot \"%s\"", grub_entry);
> +	if (system(command) != 0) {
> +		igt_debug("Failed to set GRUB boot target to: %s\n",
> +			  grub_entry);
> +		return false;
> +	}
> +
> +	igt_debug("Set GRUB to boot kernel: %s (GRUB entry: %s)\n",
> +		  current_kernel, grub_entry);
> +	return true;
> +}
> diff --git a/lib/igt_pm.h b/lib/igt_pm.h
> index 6b428f53e..7cc774e85 100644
> --- a/lib/igt_pm.h
> +++ b/lib/igt_pm.h
> @@ -97,5 +97,7 @@ uint64_t igt_pm_get_runtime_suspended_time(struct pci_device *pci_dev);
>  uint64_t igt_pm_get_runtime_active_time(struct pci_device *pci_dev);
>  int igt_pm_get_runtime_usage(struct pci_device *pci_dev);
>  void igt_pm_ignore_slpc_efficient_freq(int i915, int gtfd, bool val);
> +bool igt_pm_check_hibernation_support(void);
> +bool igt_pm_ensure_grub_boots_same_kernel(void);
>  
>  #endif /* IGT_PM_H */
> -- 
> 2.45.2
>