[External] Re: [PATCH v2 1/3] riscv: mm: Use ASID in update_mmu_cache()

[Xu Lu]

Hi Paul,

A gentle ping.

I have no idea what I can do regarding linux-next. Could you please
help revert the patch from version 1 and cherry-pick all the patches
from version 2 instead? Or what can I do for this?

Best regards,
Xu Lu

On Fri, Jul 17, 2026 at 10:11 AM Xu Lu <luxu.kernel at bytedance.com> wrote:
>
> Hi Paul,
>
> Klara found that linux-next cherry-picks the new version of patch 2
> while picking the old version of patch 1, which leads to an
> uninitialized asid. Could you please help correct this?
>
> Best regards,
> Xu Lu
>
> On Fri, Jul 17, 2026 at 12:25 AM Klara Modin <klarasmodin at gmail.com> wrote:
> >
> > Hi,
> >
> > On 2026-07-15 21:20:07 +0800, Xu Lu wrote:
> > > Only flush TLB entries for the specified mm in update_mmu_cache_range().
> > >
> > > Signed-off-by: Xu Lu <luxu.kernel at bytedance.com>
> > > ---
> > >  arch/riscv/include/asm/pgtable.h  | 4 +++-
> > >  arch/riscv/include/asm/tlbflush.h | 5 +++++
> > >  arch/riscv/mm/tlbflush.c          | 5 -----
> > >  3 files changed, 8 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> > > index 5d5756bda82e..9926556099ae 100644
> > > --- a/arch/riscv/include/asm/pgtable.h
> > > +++ b/arch/riscv/include/asm/pgtable.h
> > > @@ -568,6 +568,8 @@ static inline void update_mmu_cache_range(struct vm_fault *vmf,
> > >               struct vm_area_struct *vma, unsigned long address,
> > >               pte_t *ptep, unsigned int nr)
> > >  {
> > > +     unsigned long asid = get_mm_asid(vma->vm_mm);
> > > +
> >
> > It seems the old version of this patch is still used (at least in
> > next-202650716, 15ce1d7c4ddfe0dff00fcaee4ccaeef3efbc62c6), which means
> > asid is not initialised here. We instead have:
> >
> > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> > index 5d5756bda82e..755495a542cc 100644
> > --- a/arch/riscv/include/asm/pgtable.h
> > +++ b/arch/riscv/include/asm/pgtable.h
> > @@ -568,6 +568,8 @@ static inline void update_mmu_cache_range(struct vm_fault *vmf,
> >                 struct vm_area_struct *vma, unsigned long address,
> >                 pte_t *ptep, unsigned int nr)
> >  {
> > +       unsigned long asid;
> > +
> >         /*
> >          * Svvptc guarantees that the new valid pte will be visible within
> >          * a bounded timeframe, so when the uarch does not cache invalid
> > @@ -583,10 +585,11 @@ static inline void update_mmu_cache_range(struct vm_fault *vmf,
> >          * Relying on flush_tlb_fix_spurious_fault would suffice, but
> >          * the extra traps reduce performance.  So, eagerly SFENCE.VMA.
> >          */
> > +       asid = get_mm_asid(vma->vm_mm);
> >         while (nr--)
> > -               local_flush_tlb_page(address + nr * PAGE_SIZE);
> > -
> > +               local_flush_tlb_page_asid(address + nr * PAGE_SIZE, asid);
> >  }
> > +
> >  #define update_mmu_cache(vma, addr, ptep) \
> >         update_mmu_cache_range(NULL, vma, addr, ptep, 1)
> >
> >
> > This means that patch 2 of this series will use the uninitialised asid
> > for local_svinval_vma() and I get the same behaviour as before (hang on
> > initramfs). If I revert the two patches of this series which are in next
> > and apply this again it's fine.
> >
> > Regards,
> > Klara Modin
> >
> > >       /*
> > >        * Svvptc guarantees that the new valid pte will be visible within
> > >        * a bounded timeframe, so when the uarch does not cache invalid
> > > @@ -584,7 +586,7 @@ static inline void update_mmu_cache_range(struct vm_fault *vmf,
> > >        * the extra traps reduce performance.  So, eagerly SFENCE.VMA.
> > >        */
> > >       while (nr--)
> > > -             local_flush_tlb_page(address + nr * PAGE_SIZE);
> > > +             local_flush_tlb_page_asid(address + nr * PAGE_SIZE, asid);
> > >
> > >  }
> > >  #define update_mmu_cache(vma, addr, ptep) \
> > > diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
> > > index eed0abc40514..7c2cd5cc92d3 100644
> > > --- a/arch/riscv/include/asm/tlbflush.h
> > > +++ b/arch/riscv/include/asm/tlbflush.h
> > > @@ -15,6 +15,11 @@
> > >  #define FLUSH_TLB_NO_ASID       ((unsigned long)-1)
> > >
> > >  #ifdef CONFIG_MMU
> > > +static inline unsigned long get_mm_asid(struct mm_struct *mm)
> > > +{
> > > +     return mm ? cntx2asid(atomic_long_read(&mm->context.id)) : FLUSH_TLB_NO_ASID;
> > > +}
> > > +
> > >  static inline void local_flush_tlb_all(void)
> > >  {
> > >       __asm__ __volatile__ ("sfence.vma" : : : "memory");
> > > diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
> > > index 8404530ec00f..73c226f719c7 100644
> > > --- a/arch/riscv/mm/tlbflush.c
> > > +++ b/arch/riscv/mm/tlbflush.c
> > > @@ -110,11 +110,6 @@ static void __ipi_flush_tlb_range_asid(void *info)
> > >       local_flush_tlb_range_asid(d->start, d->size, d->stride, d->asid);
> > >  }
> > >
> > > -static inline unsigned long get_mm_asid(struct mm_struct *mm)
> > > -{
> > > -     return mm ? cntx2asid(atomic_long_read(&mm->context.id)) : FLUSH_TLB_NO_ASID;
> > > -}
> > > -
> > >  static void __flush_tlb_range(struct mm_struct *mm,
> > >                             const struct cpumask *cmask,
> > >                             unsigned long start, unsigned long size,
> > > --
> > > 2.39.5
> > >