Subject: Re: [PATCH v2 02/17] powerpc/cell: Move data segment faulting code out of cell platform

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 01 Oct 2014 15:23:16 +0530

Michael Neuling <[email-masked]> writes:

> From: Ian Munsie <[email-masked]>
>
> __spu_trap_data_seg() currently contains code to determine the VSID and ESID
> required for a particular EA and mm struct.
>
> This code is generically useful for other co-processors.  This moves the code
> of the cell platform so it can be used by other powerpc code.  It also adds 1TB
> segment handling which Cell didn't have.
>
> Signed-off-by: Ian Munsie <[email-masked]>
> Signed-off-by: Michael Neuling <[email-masked]>
> ---
>  arch/powerpc/include/asm/mmu-hash64.h  |  7 ++++-
>  arch/powerpc/mm/copro_fault.c          | 48 ++++++++++++++++++++++++++++++++++
>  arch/powerpc/mm/slb.c                  |  3 ---
>  arch/powerpc/platforms/cell/spu_base.c | 41 +++--------------------------
>  4 files changed, 58 insertions(+), 41 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/mmu-hash64.h b/arch/powerpc/include/asm/mmu-hash64.h
> index d765144..6d0b7a2 100644
> --- a/arch/powerpc/include/asm/mmu-hash64.h
> +++ b/arch/powerpc/include/asm/mmu-hash64.h
> @@ -189,7 +189,12 @@ static inline unsigned int mmu_psize_to_shift(unsigned int mmu_psize)
>  #define LP_MASK(i)	((0xFF >> (i)) << LP_SHIFT)
>  
>  #ifndef __ASSEMBLY__
> -
> +static inline int slb_vsid_shift(int ssize)
> +{
> +	if (ssize == MMU_SEGSIZE_256M)
> +		return SLB_VSID_SHIFT;
> +	return SLB_VSID_SHIFT_1T;
> +}
>  static inline int segment_shift(int ssize)
>  {
>  	if (ssize == MMU_SEGSIZE_256M)
> diff --git a/arch/powerpc/mm/copro_fault.c b/arch/powerpc/mm/copro_fault.c
> index ba7df14..b865697 100644
> --- a/arch/powerpc/mm/copro_fault.c
> +++ b/arch/powerpc/mm/copro_fault.c
> @@ -90,3 +90,51 @@ out_unlock:
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(copro_handle_mm_fault);
> +
> +int copro_data_segment(struct mm_struct *mm, u64 ea, u64 *esid, u64 *vsid)
> +{
> +	int psize, ssize;
> +
> +	*esid = (ea & ESID_MASK) | SLB_ESID_V;
> +
> +	switch (REGION_ID(ea)) {
> +	case USER_REGION_ID:
> +		pr_devel("copro_data_segment: 0x%llx -- USER_REGION_ID\n", ea);
> +#ifdef CONFIG_PPC_MM_SLICES
> +		psize = get_slice_psize(mm, ea);
> +#else
> +		psize = mm->context.user_psize;
> +#endif
> +		ssize = user_segment_size(ea);
> +		*vsid = (get_vsid(mm->context.id, ea, ssize)
> +			 << slb_vsid_shift(ssize)) | SLB_VSID_USER;
> +		break;
> +	case VMALLOC_REGION_ID:
> +		pr_devel("copro_data_segment: 0x%llx -- VMALLOC_REGION_ID\n", ea);
> +		if (ea < VMALLOC_END)
> +			psize = mmu_vmalloc_psize;
> +		else
> +			psize = mmu_io_psize;
> +		ssize = mmu_kernel_ssize;
> +		*vsid = (get_kernel_vsid(ea, mmu_kernel_ssize)
> +			 << SLB_VSID_SHIFT) | SLB_VSID_KERNEL;

why not
		*vsid = (get_kernel_vsid(ea, mmu_kernel_ssize)
			 << slb_vsid_shift(ssize)) | SLB_VSID_KERNEL;

for vmalloc and kernel region ? We could end up using 1T segments for kernel mapping too.

-aneesh