lkml.org 
[lkml]   [2014]   [Oct]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH v2 09/17] powerpc/mm: Add new hash_page_mm()
    From
    Date
    On Wed, 2014-10-01 at 15:13 +0530, Aneesh Kumar K.V wrote:
    > 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 ?

    Yeah, we found it sucky to understand. The current documentation is
    "buy benh a beer and ask him" which doesn't scale very well unless
    you're benh and you like beer.

    > Also why would one want to hash anything other
    > than current->mm ? How will this get called ?

    We are calling this on behalf of a co-processor (eg cxl). The mm this
    is currently associated with may not be running on a cpu.

    > May be they are explained in later patches. But can we also explain it
    > here.

    Ok, I'll add something (mpe had the same question).

    Mikey
    >
    > >
    > > 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
    > >
    > > --
    > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    > > the body of a message to majordomo@vger.kernel.org
    > > More majordomo info at http://vger.kernel.org/majordomo-info.html
    > > Please read the FAQ at http://www.tux.org/lkml/
    >



    \
     
     \ /
      Last update: 2014-10-02 09:41    [W:2.336 / U:2.232 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site