[PATCH v2 1/3] arm64: remove soft_restart() and friends

[Ard Biesheuvel]

On 23 March 2015 at 10:07, Ard Biesheuvel <ard.biesheuvel at linaro.org> wrote:
> The implementation of soft_restart() and its subordinate functions
> setup_mm_for_reboot(), cpu_soft_restart() and cpu_reset() have
> non-trivial dependencies on the state of the caches and the MMU,
> making them fragile from a maintenance pov. However, soft_restart()
> isn't actually called anywhere, so just remove the whole bunch.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>

Hmm, I guess kexec will be using soft_restart() so never mind this patch.

> ---
>  arch/arm64/include/asm/mmu.h         |  1 -
>  arch/arm64/include/asm/proc-fns.h    |  3 ---
>  arch/arm64/include/asm/system_misc.h |  1 -
>  arch/arm64/kernel/process.c          | 12 +-----------
>  arch/arm64/mm/mmu.c                  | 11 -----------
>  arch/arm64/mm/proc.S                 | 33 ---------------------------------
>  6 files changed, 1 insertion(+), 60 deletions(-)
>
> diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
> index 3d311761e3c2..99064c075fc6 100644
> --- a/arch/arm64/include/asm/mmu.h
> +++ b/arch/arm64/include/asm/mmu.h
> @@ -28,7 +28,6 @@ typedef struct {
>  #define ASID(mm)       ((mm)->context.id & 0xffff)
>
>  extern void paging_init(void);
> -extern void setup_mm_for_reboot(void);
>  extern void __iomem *early_io_map(phys_addr_t phys, unsigned long virt);
>  extern void init_mem_pgprot(void);
>  extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
> diff --git a/arch/arm64/include/asm/proc-fns.h b/arch/arm64/include/asm/proc-fns.h
> index 4d9ede7b6361..ab334467c6a4 100644
> --- a/arch/arm64/include/asm/proc-fns.h
> +++ b/arch/arm64/include/asm/proc-fns.h
> @@ -31,9 +31,6 @@ struct cpu_suspend_ctx;
>  extern void cpu_cache_off(void);
>  extern void cpu_do_idle(void);
>  extern void cpu_do_switch_mm(unsigned long pgd_phys, struct mm_struct *mm);
> -extern void cpu_reset(unsigned long addr) __attribute__((noreturn));
> -void cpu_soft_restart(phys_addr_t cpu_reset,
> -               unsigned long addr) __attribute__((noreturn));
>  extern void cpu_do_suspend(struct cpu_suspend_ctx *ptr);
>  extern u64 cpu_do_resume(phys_addr_t ptr, u64 idmap_ttbr);
>
> diff --git a/arch/arm64/include/asm/system_misc.h b/arch/arm64/include/asm/system_misc.h
> index 7a18fabbe0f6..659fbf5925de 100644
> --- a/arch/arm64/include/asm/system_misc.h
> +++ b/arch/arm64/include/asm/system_misc.h
> @@ -41,7 +41,6 @@ struct mm_struct;
>  extern void show_pte(struct mm_struct *mm, unsigned long addr);
>  extern void __show_regs(struct pt_regs *);
>
> -void soft_restart(unsigned long);
>  extern void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
>
>  #define UDBG_UNDEFINED (1 << 0)
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index c6b1f3b96f45..c506bee6b613 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -58,14 +58,6 @@ unsigned long __stack_chk_guard __read_mostly;
>  EXPORT_SYMBOL(__stack_chk_guard);
>  #endif
>
> -void soft_restart(unsigned long addr)
> -{
> -       setup_mm_for_reboot();
> -       cpu_soft_restart(virt_to_phys(cpu_reset), addr);
> -       /* Should never get here */
> -       BUG();
> -}
> -
>  /*
>   * Function pointers to optional machine specific functions
>   */
> @@ -136,9 +128,7 @@ void machine_power_off(void)
>
>  /*
>   * Restart requires that the secondary CPUs stop performing any activity
> - * while the primary CPU resets the system. Systems with a single CPU can
> - * use soft_restart() as their machine descriptor's .restart hook, since that
> - * will cause the only available CPU to reset. Systems with multiple CPUs must
> + * while the primary CPU resets the system. Systems with multiple CPUs must
>   * provide a HW restart implementation, to ensure that all CPUs reset at once.
>   * This is required so that any code running after reset on the primary CPU
>   * doesn't have to co-ordinate with other CPUs to ensure they aren't still
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 428aaf86c95b..15ac396229d5 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -460,17 +460,6 @@ void __init paging_init(void)
>  }
>
>  /*
> - * Enable the identity mapping to allow the MMU disabling.
> - */
> -void setup_mm_for_reboot(void)
> -{
> -       cpu_set_reserved_ttbr0();
> -       flush_tlb_all();
> -       cpu_set_idmap_tcr_t0sz();
> -       cpu_switch_mm(idmap_pg_dir, &init_mm);
> -}
> -
> -/*
>   * Check whether a kernel address is valid (derived from arch/x86/).
>   */
>  int kern_addr_valid(unsigned long addr)
> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> index cdd754e19b9b..a2059ec61463 100644
> --- a/arch/arm64/mm/proc.S
> +++ b/arch/arm64/mm/proc.S
> @@ -59,39 +59,6 @@ ENTRY(cpu_cache_off)
>  ENDPROC(cpu_cache_off)
>
>  /*
> - *     cpu_reset(loc)
> - *
> - *     Perform a soft reset of the system.  Put the CPU into the same state
> - *     as it would be if it had been reset, and branch to what would be the
> - *     reset vector. It must be executed with the flat identity mapping.
> - *
> - *     - loc   - location to jump to for soft reset
> - */
> -       .align  5
> -ENTRY(cpu_reset)
> -       mrs     x1, sctlr_el1
> -       bic     x1, x1, #1
> -       msr     sctlr_el1, x1                   // disable the MMU
> -       isb
> -       ret     x0
> -ENDPROC(cpu_reset)
> -
> -ENTRY(cpu_soft_restart)
> -       /* Save address of cpu_reset() and reset address */
> -       mov     x19, x0
> -       mov     x20, x1
> -
> -       /* Turn D-cache off */
> -       bl      cpu_cache_off
> -
> -       /* Push out all dirty data, and ensure cache is empty */
> -       bl      flush_cache_all
> -
> -       mov     x0, x20
> -       ret     x19
> -ENDPROC(cpu_soft_restart)
> -
> -/*
>   *     cpu_do_idle()
>   *
>   *     Idle the processor (wait for interrupt).
> --
> 1.8.3.2
>