Re: [PATCH 04/10] arm64: Add EL2 switch to soft_restart

[Mark Rutland <mark.rutland@arm.com>]

On Fri, Oct 24, 2014 at 12:10:58AM +0100, Geoff Levand wrote:
> When a CPU is reset it needs to be put into the exception level it had when it
> entered the kernel.  Update cpu_reset() to accept an argument el2_switch which
> signals cpu_reset() to enter the soft reset address at EL2.  If el2_switch is
> not set the soft reset address will be entered at EL1.
> 
> Update cpu_soft_restart() and soft_restart() to pass the return of
> is_hyp_mode_available() as the el2_switch value to cpu_reset().  Also update the
> comments of cpu_reset(), cpu_soft_restart() and soft_restart() to reflect this
> change.

This will blow up without warning with KVM, and I think we need to
address that first.

Mark.

> Signed-off-by: Geoff Levand <geoff@infradead.org>
> ---
>  arch/arm64/include/asm/proc-fns.h |  4 ++--
>  arch/arm64/kernel/process.c       |  6 ++++-
>  arch/arm64/mm/proc.S              | 47 +++++++++++++++++++++++++++++----------
>  3 files changed, 42 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/proc-fns.h b/arch/arm64/include/asm/proc-fns.h
> index 9a8fd84..339394d 100644
> --- a/arch/arm64/include/asm/proc-fns.h
> +++ b/arch/arm64/include/asm/proc-fns.h
> @@ -32,8 +32,8 @@ 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));
> +void cpu_soft_restart(phys_addr_t cpu_reset, unsigned long el2_switch,
> +		      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/kernel/process.c b/arch/arm64/kernel/process.c
> index bf66922..0a3414b 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -50,6 +50,7 @@
>  #include <asm/mmu_context.h>
>  #include <asm/processor.h>
>  #include <asm/stacktrace.h>
> +#include <asm/virt.h>
>  
>  #ifdef CONFIG_CC_STACKPROTECTOR
>  #include <linux/stackprotector.h>
> @@ -60,7 +61,10 @@ EXPORT_SYMBOL(__stack_chk_guard);
>  void soft_restart(unsigned long addr)
>  {
>  	setup_mm_for_reboot();
> -	cpu_soft_restart(virt_to_phys(cpu_reset), addr);
> +
> +	cpu_soft_restart(virt_to_phys(cpu_reset), is_hyp_mode_available(),
> +			 addr);
> +
>  	/* Should never get here */
>  	BUG();
>  }
> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> index 4e778b1..7467199 100644
> --- a/arch/arm64/mm/proc.S
> +++ b/arch/arm64/mm/proc.S
> @@ -25,6 +25,7 @@
>  #include <asm/hwcap.h>
>  #include <asm/pgtable-hwdef.h>
>  #include <asm/pgtable.h>
> +#include <asm/virt.h>
>  
>  #include "proc-macros.S"
>  
> @@ -59,27 +60,48 @@ ENTRY(cpu_cache_off)
>  ENDPROC(cpu_cache_off)
>  
>  /*
> - *	cpu_reset(loc)
> + * cpu_reset(el2_switch, loc) - Helper for cpu_soft_restart.
>   *
> - *	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.
> + * @cpu_reset: Physical address of the cpu_reset routine.
> + * @el2_switch: Flag to indicate a swich to EL2 is needed.
> + * @addr: Location to jump to for soft reset.
>   *
> - *	- loc   - location to jump to for soft reset
> + * 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.
>   */
> +
>  	.align	5
> +
>  ENTRY(cpu_reset)
> -	mrs	x1, sctlr_el1
> -	bic	x1, x1, #1
> -	msr	sctlr_el1, x1			// disable the MMU
> +	mrs	x2, sctlr_el1
> +	bic	x2, x2, #1
> +	msr	sctlr_el1, x2			// disable the MMU
>  	isb
> -	ret	x0
> +
> +	cbz	x0, 1f				// el2_switch?
> +	mov	x0, x1
> +	mov	x1, xzr
> +	mov	x2, xzr
> +	mov	x3, xzr
> +	hvc	#HVC_CALL_FUNC			// no return
> +
> +1:	ret	x1
>  ENDPROC(cpu_reset)
>  
> +/*
> + * cpu_soft_restart(cpu_reset, el2_switch, addr) - Perform a cpu soft reset.
> + *
> + * @cpu_reset: Physical address of the cpu_reset routine.
> + * @el2_switch: Flag to indicate a swich to EL2 is needed, passed to cpu_reset.
> + * @addr: Location to jump to for soft reset, passed to cpu_reset.
> + *
> + */
> +
>  ENTRY(cpu_soft_restart)
> -	/* Save address of cpu_reset() and reset address */
> -	mov	x19, x0
> -	mov	x20, x1
> +	mov	x19, x0				// cpu_reset
> +	mov	x20, x1				// el2_switch
> +	mov	x21, x2				// addr
>  
>  	/* Turn D-cache off */
>  	bl	cpu_cache_off
> @@ -88,6 +110,7 @@ ENTRY(cpu_soft_restart)
>  	bl	flush_cache_all
>  
>  	mov	x0, x20
> +	mov	x1, x21
>  	ret	x19
>  ENDPROC(cpu_soft_restart)
>  
> -- 
> 1.9.1
> 
> 
> 
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> 

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