linux-kernel - Re: [PATCH] riscv: mm: Fix incorrect ASID argument when flushing TLB

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Date:   Mon, 13 Mar 2023 11:32:27 +0800
From:   Dylan Jhong <dylan@...estech.com>
To:     Guo Ren <guoren@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-riscv@...ts.infradead.org>,
        <sergey.matyukevich@...tacore.com>, <aou@...s.berkeley.edu>,
        <palmer@...belt.com>, <paul.walmsley@...ive.com>,
        <x5710999x@...il.com>, <tim609@...estech.com>,
        <peterlin@...estech.com>, <ycliang@...estech.com>
Subject: Re: [PATCH] riscv: mm: Fix incorrect ASID argument when flushing TLB

On Sun, Mar 12, 2023 at 08:40:59PM +0800, Guo Ren wrote:
> On Fri, Mar 10, 2023 at 6:32 PM Dylan Jhong <dylan@...estech.com> wrote:
> >
> > Currently, we pass the CONTEXTID instead of the ASID to the TLB flush
> > function. We should only take the ASID field to prevent from touching
> > the reserved bit field.
> >
> > Fixes: 3f1e782998cd ("riscv: add ASID-based tlbflushing methods")
> > Signed-off-by: Dylan Jhong <dylan@...estech.com>
> > ---
> >  arch/riscv/include/asm/tlbflush.h | 2 ++
> >  arch/riscv/mm/context.c           | 3 ++-
> >  arch/riscv/mm/tlbflush.c          | 2 +-
> >  3 files changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
> > index 907b9efd39a8..597d6d8aec28 100644
> > --- a/arch/riscv/include/asm/tlbflush.h
> > +++ b/arch/riscv/include/asm/tlbflush.h
> > @@ -12,6 +12,8 @@
> >  #include <asm/errata_list.h>
> >
> >  #ifdef CONFIG_MMU
> > +extern unsigned long asid_mask;
> > +
> >  static inline void local_flush_tlb_all(void)
> >  {
> >         __asm__ __volatile__ ("sfence.vma" : : : "memory");
> > diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c
> > index 80ce9caba8d2..a6b76b33e377 100644
> > --- a/arch/riscv/mm/context.c
> > +++ b/arch/riscv/mm/context.c
> > @@ -22,7 +22,8 @@ DEFINE_STATIC_KEY_FALSE(use_asid_allocator);
> >
> >  static unsigned long asid_bits;
> >  static unsigned long num_asids;
> > -static unsigned long asid_mask;
> > +unsigned long asid_mask;
> > +EXPORT_SYMBOL(asid_mask);
> Why EXPORT_SYMBOL? (No module would use it by your patch.)
>
OK. I'll remove EXPORT_SYMBOL in v2.
Thanks.

> >
> >  static atomic_long_t current_version;
> >
> > diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
> > index ce7dfc81bb3f..ba4c27187c95 100644
> > --- a/arch/riscv/mm/tlbflush.c
> > +++ b/arch/riscv/mm/tlbflush.c
> > @@ -27,7 +27,7 @@ static void __sbi_tlb_flush_range(struct mm_struct *mm, unsigned long start,
> >         /* check if the tlbflush needs to be sent to other CPUs */
> >         broadcast = cpumask_any_but(cmask, cpuid) < nr_cpu_ids;
> >         if (static_branch_unlikely(&use_asid_allocator)) {
> > -               unsigned long asid = atomic_long_read(&mm->context.id);
> > +               unsigned long asid = atomic_long_read(&mm->context.id) & asid_mask;
> >
> >                 /*
> >                  * TLB will be immediately flushed on harts concurrently
> > --
> > 2.34.1
> >
> 
> 
> -- 
> Best Regards
>  Guo Ren