Re: [PATCH v3 3/4] mm: rmap: Extend tlbbatch APIs to fit new platforms

[Barry Song <21cnbao@gmail.com>]

On Fri, Sep 9, 2022 at 4:51 PM Anshuman Khandual
<anshuman.khandual@arm.com> wrote:
>
>
>
> On 8/22/22 13:51, Yicong Yang wrote:
> > From: Barry Song <v-songbaohua@oppo.com>
> >
> > Add uaddr to tlbbatch APIs so that platforms like ARM64 are
>
> I guess 'uaddr' refers to a virtual address from the process address
> space itself ? Please be more specific.
>
> > able to apply this on their specific hardware features. For
> > ARM64, this could be sending tlbi into hardware queues for
> > the page with this particular uaddr.
>
> This subject line and commit message here are misleading. The patch
> adds an address argument to arch callback arch_tlbbatch_add_mm() as
> arm64 platform could use that to perform the TLB flush batching ?
>
> This patch can be folded into the next one, so that the requirement
> for an additional argument 'uaddr' in the arch callback will be self
> evident. OR if this is going to be a preparatory patch, then it must
> explain how 'uaddr' argument is helpful on platforms like arm64 while
> performing TLB flush batching. But TBH, just folding it to next patch
> explains the context better.

The intention was to keep each change small, while still functionally
independent,
so that it was easier to be reviewed.

but yes, i agree in this particular case, if we fold this one to the
last one, we are
actually able to make the modification self-evident while the new patch seems
still small.

>
> >
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Borislav Petkov <bp@alien8.de>
> > Cc: Dave Hansen <dave.hansen@linux.intel.com>
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: Nadav Amit <namit@vmware.com>
> > Cc: Mel Gorman <mgorman@suse.de>
> > Tested-by: Xin Hao <xhao@linux.alibaba.com>
> > Signed-off-by: Barry Song <v-songbaohua@oppo.com>
> > Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
> > ---
> >  arch/x86/include/asm/tlbflush.h |  3 ++-
> >  mm/rmap.c                       | 10 ++++++----
> >  2 files changed, 8 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
> > index 8a497d902c16..5bd78ae55cd4 100644
> > --- a/arch/x86/include/asm/tlbflush.h
> > +++ b/arch/x86/include/asm/tlbflush.h
> > @@ -264,7 +264,8 @@ static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
> >  }
> >
> >  static inline void arch_tlbbatch_add_mm(struct arch_tlbflush_unmap_batch *batch,
> > -                                     struct mm_struct *mm)
> > +                                     struct mm_struct *mm,
> > +                                     unsigned long uaddr)
> >  {
> >       inc_mm_tlb_gen(mm);
> >       cpumask_or(&batch->cpumask, &batch->cpumask, mm_cpumask(mm));
> > diff --git a/mm/rmap.c b/mm/rmap.c
> > index a17a004550c6..7187a72b63b1 100644
> > --- a/mm/rmap.c
> > +++ b/mm/rmap.c
> > @@ -642,12 +642,13 @@ void try_to_unmap_flush_dirty(void)
> >  #define TLB_FLUSH_BATCH_PENDING_LARGE                        \
> >       (TLB_FLUSH_BATCH_PENDING_MASK / 2)
> >
> > -static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
> > +static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable,
> > +                                   unsigned long uaddr)
> >  {
> >       struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
> >       int batch, nbatch;
> >
> > -     arch_tlbbatch_add_mm(&tlb_ubc->arch, mm);
> > +     arch_tlbbatch_add_mm(&tlb_ubc->arch, mm, uaddr);
> >       tlb_ubc->flush_required = true;
> >
> >       /*
> > @@ -725,7 +726,8 @@ void flush_tlb_batched_pending(struct mm_struct *mm)
> >       }
> >  }
> >  #else
> > -static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
> > +static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable,
> > +                                   unsigned long uaddr)
> >  {
> >  }
> >
> > @@ -1587,7 +1589,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
> >                                */
> >                               pteval = ptep_get_and_clear(mm, address, pvmw.pte);
> >
> > -                             set_tlb_ubc_flush_pending(mm, pte_dirty(pteval));
> > +                             set_tlb_ubc_flush_pending(mm, pte_dirty(pteval), address);
> >                       } else {
> >                               pteval = ptep_clear_flush(vma, address, pvmw.pte);
> >                       }

Thanks
Barry