Re: [Xen-devel] [RFC for-4.5 2/5] xen/arm32: Introduce lookup_processor_type

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-02-11 at 20:04 +0000, Julien Grall wrote:
> Looking for a specific proc_info structure is already implemented in assembly.
> Implement lookup_processor_type to avoid duplicate code between C and
> assembly.
> 
> This function searches the proc_info_list structure following the processor
> ID. If the search fail, it will return NULL, otherwise a pointer to this
> structure for the specific processor.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

> ---
>  xen/arch/arm/arm32/head.S |   57 
> ++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 43 insertions(+), 14 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 77f5518..68fb499 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -198,26 +198,16 @@ skip_bss:
>          PRINT("- Setting up control registers -\r\n")
>  
>          /* Get processor specific proc info into r1 */
> -        mrc   CP32(r0, MIDR)                /* r0 := our cpu id */
> -        ldr   r1, = __proc_info_start
> -        add   r1, r1, r10                   /* r1 := paddr of table (start) 
> */
> -        ldr   r2, = __proc_info_end
> -        add   r2, r2, r10                   /* r2 := paddr of table (end) */
> -1:      ldr   r3, [r1, #PROCINFO_cpu_mask]
> -        and   r4, r0, r3                    /* r4 := our cpu id with mask */
> -        ldr   r3, [r1, #PROCINFO_cpu_val]   /* r3 := cpu val in current proc 
> info */
> -        teq   r4, r3
> -        beq   2f                            /* Match => exit, or try next 
> proc info */
> -        add   r1, r1, #PROCINFO_sizeof
> -        cmp   r1, r2
> -        blo   1b
> +        bl    __lookup_processor_type
> +        teq   r1, #0
> +        bne   1f
>          mov   r4, r0
>          PRINT("- Missing processor info: ")
>          mov   r0, r4
>          bl    putn
>          PRINT(" -\r\n")
>          b     fail
> -2:
> +1:
>  
>          /* Jump to cpu_init */
>          ldr   r1, [r1, #PROCINFO_cpu_init]  /* r1 := vaddr(init func) */
> @@ -545,6 +535,45 @@ putn:   mov   pc, lr
>  
>  #endif /* !CONFIG_EARLY_PRINTK */
>  
> +/* This provides a C-API version of __lookup_processor_type */
> +GLOBAL(lookup_processor_type)
> +        stmfd sp!, {r4, r10, lr}
> +        mov   r10, #0                   /* r10 := offset between virt&phys */
> +        bl    __lookup_processor_type
> +        mov r0, r1
> +        ldmfd sp!, {r4, r10, pc}
> +
> +/* Read processor ID register (CP#15, CR0), and Look up in the linker-built
> + * supported processor list. Note that we can't use the absolute addresses 
> for
> + * the __proc_info lists since we aren't running with the MMU on (and 
> therefore,
> + * we are not in correct address space). We have to calculate the offset.
> + *
> + * r10: offset between virt&phys
> + *
> + * Returns:
> + * r0: CPUID
> + * r1: proc_info pointer
> + * Clobbers r2-r4
> + */
> +__lookup_processor_type:
> +        mrc   CP32(r0, MIDR)                /* r0 := our cpu id */
> +        ldr   r1, = __proc_info_start
> +        add   r1, r1, r10                   /* r1 := paddr of table (start) 
> */
> +        ldr   r2, = __proc_info_end
> +        add   r2, r2, r10                   /* r2 := paddr of table (end) */
> +1:      ldr   r3, [r1, #PROCINFO_cpu_mask]
> +        and   r4, r0, r3                    /* r4 := our cpu id with mask */
> +        ldr   r3, [r1, #PROCINFO_cpu_val]   /* r3 := cpu val in current proc 
> info */
> +        teq   r4, r3
> +        beq   2f                            /* Match => exit, or try next 
> proc info */
> +        add   r1, r1, #PROCINFO_sizeof
> +        cmp   r1, r2
> +        blo   1b
> +        /* We failed to find the proc_info, return NULL */
> +        mov   r1, #0
> +2:
> +        mov   pc, lr
> +
>  /*
>   * Local variables:
>   * mode: ASM



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