Re: [PATCH v2 09/17] powerpc/mm: Add new hash_page_mm()

Aneesh Kumar K.V
2014-10-01T09:44:18Z

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.

It would be nice to document the rules here. So when we try to add a hash
page entry, and if that result in demotion of the segment are we suppose to
flush slbs ? Also why would one want to hash anything other
than current->mm ? How will this get called ?

May be they are explained in later patches. But can we also explain it
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 | 22 ++++++++++++++--------
> 2 files changed, 15 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/mmu-hash64.h b/arch/powerpc/include/asm/mmu-hash64.h
> index 6d0b7a2..f84e5a5 100644
> --- a/arch/powerpc/include/asm/mmu-hash64.h
> +++ b/arch/powerpc/include/asm/mmu-hash64.h
> @@ -322,6 +322,7 @@ 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 bbdb054..0a5c8c0 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -904,7 +904,7 @@ void demote_segment_4k(struct mm_struct *mm, unsigned long addr)
> return;
> slice_set_range_psize(mm, addr, 1, MMU_PAGE_4K);
> copro_flush_all_slbs(mm);
> - if (get_paca_psize(addr) != MMU_PAGE_4K) {
> + if ((get_paca_psize(addr) != MMU_PAGE_4K) && (current->mm == mm)) {
> get_paca()->context = mm->context;
> slb_flush_and_rebolt();
> }
> @@ -989,26 +989,24 @@ 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;
> @@ -1104,7 +1102,8 @@ 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;
> }
> @@ -1145,7 +1144,8 @@ 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
> @@ -1180,6 +1180,12 @@ 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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