linux-kernel - Re: [PATCH 1/2] efi/reboot: Add support for EFI_RESET_PLATFORM

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Message-ID: <CAMj1kXEsJMp8O-BckAoizDQRyirbZN+jYjYF9GGga4kd30em=A@mail.gmail.com>
Date: Fri, 14 Nov 2025 22:41:10 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Sumit Garg <sumit.garg@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-efi@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, catalin.marinas@....com, will@...nel.org, 
	mark.rutland@....com, andersson@...nel.org, konradybcio@...nel.org, 
	dmitry.baryshkov@....qualcomm.com, shivendra.pratap@....qualcomm.com, 
	leif.lindholm@....qualcomm.com, linux-kernel@...r.kernel.org, 
	Sumit Garg <sumit.garg@....qualcomm.com>
Subject: Re: [PATCH 1/2] efi/reboot: Add support for EFI_RESET_PLATFORM_SPECIFIC

On Fri, 14 Nov 2025 at 09:51, Sumit Garg <sumit.garg@...nel.org> wrote:
>
> From: Sumit Garg <sumit.garg@....qualcomm.com>
>
> UEFI specification provides support for EfiResetPlatformSpecific reset
> type as follows:
>
> "
> ResetSystem:
>
> Calling this interface with ResetType of EfiResetPlatformSpecific
> causes a system-wide reset. The exact type of the reset is defined
> by the EFI_GUID that follows the Null-terminated Unicode string passed
> into ResetData. If the platform does not recognize the EFI_GUID in
> ResetData the platform must pick a supported reset type to perform.
> The platform may optionally log the parameters from any non-normal
> reset that occurs.
> "
>
> Lets use the ResetData to pass the platform specific reboot command
> issued and leave it's interpretation to UEFI implementation following
> the specification.
>
> Signed-off-by: Sumit Garg <sumit.garg@....qualcomm.com>
> ---
>  drivers/firmware/efi/reboot.c | 25 +++++++++++++++----------
>  include/linux/efi.h           |  5 +++--
>  2 files changed, 18 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/firmware/efi/reboot.c b/drivers/firmware/efi/reboot.c
> index ceae84c19d22..23a2fc68e9c9 100644
> --- a/drivers/firmware/efi/reboot.c
> +++ b/drivers/firmware/efi/reboot.c
> @@ -10,7 +10,7 @@ static struct sys_off_handler *efi_sys_off_handler;
>
>  int efi_reboot_quirk_mode = -1;
>
> -void efi_reboot(enum reboot_mode reboot_mode, const char *__unused)
> +void efi_reboot(enum reboot_mode reboot_mode, const char *data)
>  {
>         const char *str[] = { "cold", "warm", "shutdown", "platform" };
>         int efi_mode, cap_reset_mode;
> @@ -18,14 +18,18 @@ void efi_reboot(enum reboot_mode reboot_mode, const char *__unused)
>         if (!efi_rt_services_supported(EFI_RT_SUPPORTED_RESET_SYSTEM))
>                 return;
>
> -       switch (reboot_mode) {
> -       case REBOOT_WARM:
> -       case REBOOT_SOFT:
> -               efi_mode = EFI_RESET_WARM;
> -               break;
> -       default:
> -               efi_mode = EFI_RESET_COLD;
> -               break;
> +       if (data) {
> +               efi_mode = EFI_RESET_PLATFORM_SPECIFIC;
> +       } else {
> +               switch (reboot_mode) {
> +               case REBOOT_WARM:
> +               case REBOOT_SOFT:
> +                       efi_mode = EFI_RESET_WARM;
> +                       break;
> +               default:
> +                       efi_mode = EFI_RESET_COLD;
> +                       break;
> +               }
>         }
>
>         /*
> @@ -43,7 +47,8 @@ void efi_reboot(enum reboot_mode reboot_mode, const char *__unused)
>                 efi_mode = cap_reset_mode;
>         }
>
> -       efi.reset_system(efi_mode, EFI_SUCCESS, 0, NULL);
> +       efi.reset_system(efi_mode, EFI_SUCCESS, sizeof(data),

You cannot use sizeof() here - it will return the size of a pointer to
const char.


> +                        (efi_char16_t *)data);
>  }
>
>  bool __weak efi_poweroff_required(void)
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index a98cc39e7aaa..5324db1518b6 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -256,6 +256,7 @@ typedef union efi_boot_services efi_boot_services_t;
>  #define EFI_RESET_COLD 0
>  #define EFI_RESET_WARM 1
>  #define EFI_RESET_SHUTDOWN 2
> +#define EFI_RESET_PLATFORM_SPECIFIC 3
>
>  /*
>   * EFI Runtime Services table
> @@ -874,7 +875,7 @@ static inline bool efi_enabled(int feature)
>  {
>         return test_bit(feature, &efi.flags) != 0;
>  }
> -extern void efi_reboot(enum reboot_mode reboot_mode, const char *__unused);
> +extern void efi_reboot(enum reboot_mode reboot_mode, const char *data);
>
>  bool __pure __efi_soft_reserve_enabled(void);
>
> @@ -895,7 +896,7 @@ static inline bool efi_enabled(int feature)
>         return false;
>  }
>  static inline void
> -efi_reboot(enum reboot_mode reboot_mode, const char *__unused) {}
> +efi_reboot(enum reboot_mode reboot_mode, const char *data) {}
>
>  static inline bool efi_soft_reserve_enabled(void)
>  {
> --
> 2.48.1
>