[08/15] powerpc/mm: Add new hash_page_mm()

From: Ian Munsie <imunsie@au1.ibm.com>

This adds a new function hash_page_mm() based on the existing hash_page().
This version allows any struct mm to be passed in, rather than assuming
current.  This is useful for servicing co-processor faults which are not in the
context of the current running process.

We need to be careful here as the current hash_page() assumes current in a few
places.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Neuling <mikey@neuling.org>
---
 arch/powerpc/include/asm/mmu-hash64.h |  1 +
 arch/powerpc/mm/hash_utils_64.c       | 20 +++++++++++++-------
 2 files changed, 14 insertions(+), 7 deletions(-)

Michael Neuling <mikey@neuling.org> writes:

> From: Ian Munsie <imunsie@au1.ibm.com>
>
> This adds a new function hash_page_mm() based on the existing hash_page().
> This version allows any struct mm to be passed in, rather than assuming
> current.  This is useful for servicing co-processor faults which are not in the
> context of the current running process.
>
> We need to be careful here as the current hash_page() assumes current in a few
> places.

Can you also explain calling semantics. ie, why would we want to call
this with anything other than current ? Should we flush slb now or
should it be skipped ? so what would happen if the new hash page can
result in segment demotion ?  You don't put that under if (mm ==
current->mm). is that ok ?

	if ((pte_val(*ptep) & _PAGE_4K_PFN) && psize == MMU_PAGE_64K) {
		demote_segment_4k(mm, ea);
		psize = MMU_PAGE_4K;
	}

We also update paca context there

	if (get_paca_psize(addr) != MMU_PAGE_4K) {
		get_paca()->context = mm->context;
		slb_flush_and_rebolt();
	}


You also added code to handle KERNEL_REGION_ID in
[PATCH 02/15] powerpc/cell: Move data segment faulting code out of cell
platform. do we need to handle that here ?


>
> Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
> Signed-off-by: Michael Neuling <mikey@neuling.org>
> ---
>  arch/powerpc/include/asm/mmu-hash64.h |  1 +
>  arch/powerpc/mm/hash_utils_64.c       | 20 +++++++++++++-------
>  2 files changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/mmu-hash64.h b/arch/powerpc/include/asm/mmu-hash64.h
> index fd19a53..a3b85e9 100644
> --- a/arch/powerpc/include/asm/mmu-hash64.h
> +++ b/arch/powerpc/include/asm/mmu-hash64.h
> @@ -319,6 +319,7 @@ extern int __hash_page_64K(unsigned long ea, unsigned long access,
>  			   unsigned int local, int ssize);
>  struct mm_struct;
>  unsigned int hash_page_do_lazy_icache(unsigned int pp, pte_t pte, int trap);
> +extern int hash_page_mm(struct mm_struct *mm, unsigned long ea, unsigned long access, unsigned long trap);
>  extern int hash_page(unsigned long ea, unsigned long access, unsigned long trap);
>  int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
>  		     pte_t *ptep, unsigned long trap, int local, int ssize,
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index 0f73367..66071af 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -991,26 +991,24 @@ static void check_paca_psize(unsigned long ea, struct mm_struct *mm,
>   * -1 - critical hash insertion error
>   * -2 - access not permitted by subpage protection mechanism
>   */
> -int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
> +int hash_page_mm(struct mm_struct *mm, unsigned long ea, unsigned long access, unsigned long trap)
>  {
>  	enum ctx_state prev_state = exception_enter();
>  	pgd_t *pgdir;
>  	unsigned long vsid;
> -	struct mm_struct *mm;
>  	pte_t *ptep;
>  	unsigned hugeshift;
>  	const struct cpumask *tmp;
>  	int rc, user_region = 0, local = 0;
>  	int psize, ssize;
>  
> -	DBG_LOW("hash_page(ea=%016lx, access=%lx, trap=%lx\n",
> -		ea, access, trap);
> +	DBG_LOW("%s(ea=%016lx, access=%lx, trap=%lx\n",
> +		__func__, ea, access, trap);
>  
>  	/* Get region & vsid */
>   	switch (REGION_ID(ea)) {
>  	case USER_REGION_ID:
>  		user_region = 1;
> -		mm = current->mm;
>  		if (! mm) {
>  			DBG_LOW(" user region with no mm !\n");
>  			rc = 1;
> @@ -1106,7 +1104,8 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
>  			WARN_ON(1);
>  		}
>  #endif
> -		check_paca_psize(ea, mm, psize, user_region);
> +		if (current->mm == mm)
> +			check_paca_psize(ea, mm, psize, user_region);
>  
>  		goto bail;
>  	}
> @@ -1149,7 +1148,8 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
>  		}
>  	}
>  
> -	check_paca_psize(ea, mm, psize, user_region);
> +	if (current->mm == mm)
> +		check_paca_psize(ea, mm, psize, user_region);
>  #endif /* CONFIG_PPC_64K_PAGES */
>  
>  #ifdef CONFIG_PPC_HAS_HASH_64K
> @@ -1184,6 +1184,12 @@ bail:
>  	exception_exit(prev_state);
>  	return rc;
>  }
> +EXPORT_SYMBOL_GPL(hash_page_mm);
> +
> +int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
> +{
> +	return hash_page_mm(current->mm, ea, access, trap);
> +}
>  EXPORT_SYMBOL_GPL(hash_page);
>  
>  void hash_preload(struct mm_struct *mm, unsigned long ea,
> -- 
> 1.9.1
>
> --
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> > You also added code to handle KERNEL_REGION_ID in
> > [PATCH 02/15] powerpc/cell: Move data segment faulting code out of cell
> > platform. do we need to handle that here ?
> > 

(Sorry missed this on my other reply...)

I've refactored that code now so it should be handled in the vsid
calculation.  It's not my strong area so you might wanna check on
repost.

Thanks again.

Mikey