linux-kernel - Re: [PATCH 1/3] riscv: Improve PTDUMP to show RSW with non-zero value

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Message-ID: <ZQJavHfMLDXBaRC-@APC323>
Date:   Thu, 14 Sep 2023 08:58:36 +0800
From:   Yu-Chien Peter Lin <peterlin@...estech.com>
To:     Alexandre Ghiti <alexghiti@...osinc.com>
CC:     <paul.walmsley@...ive.com>, <palmer@...belt.com>,
        <aou@...s.berkeley.edu>, <david@...hat.com>,
        <akpm@...ux-foundation.org>, <bjorn@...osinc.com>,
        <linux-riscv@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <ycliang@...estech.com>
Subject: Re: [PATCH 1/3] riscv: Improve PTDUMP to show RSW with non-zero value

On Wed, Sep 13, 2023 at 09:29:11PM +0200, Alexandre Ghiti wrote:
> Hi Yu,
> 
> On Wed, Sep 13, 2023 at 6:25 PM Yu Chien Peter Lin
> <peterlin@...estech.com> wrote:
> >
> > RSW field is allowed to encode 2 bits of information, currently
> > PTDUMP only prints RSW when its value is 1 or 3.
> >
> > To fix this issue and enhance the debug experience with PTDUMP,
> > allow it to print the RSW with any non-zero value, otherwise,
> > it will print a empty string for each row.
> >
> > This patch also removes the val from the struct prot_bits
> > as it is no longer needed.
> >
> > Signed-off-by: Yu Chien Peter Lin <peterlin@...estech.com>
> > ---
> >  arch/riscv/include/asm/pgtable-bits.h |  2 +-
> >  arch/riscv/mm/ptdump.c                | 33 ++++++++++++---------------
> >  2 files changed, 15 insertions(+), 20 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/pgtable-bits.h b/arch/riscv/include/asm/pgtable-bits.h
> > index f896708e8331..d5e828b7d7c6 100644
> > --- a/arch/riscv/include/asm/pgtable-bits.h
> > +++ b/arch/riscv/include/asm/pgtable-bits.h
> > @@ -16,7 +16,7 @@
> >  #define _PAGE_GLOBAL    (1 << 5)    /* Global */
> >  #define _PAGE_ACCESSED  (1 << 6)    /* Set by hardware on any access */
> >  #define _PAGE_DIRTY     (1 << 7)    /* Set by hardware on any write */
> > -#define _PAGE_SOFT      (1 << 8)    /* Reserved for software */
> > +#define _PAGE_SOFT      (3 << 8)    /* Reserved for software */
> 
> That makes the PAGE_SPECIAL below use the 2 software reserved bits
> right? You should redefine PAGE_SPECIAL to (1 << 8).

Hi Alexandre,

Sure, will fix.
Thanks for the review.

Regards,
Peter Lin

> >
> >  #define _PAGE_SPECIAL   _PAGE_SOFT
> >  #define _PAGE_TABLE     _PAGE_PRESENT
> > diff --git a/arch/riscv/mm/ptdump.c b/arch/riscv/mm/ptdump.c
> > index 20a9f991a6d7..62bbea17d475 100644
> > --- a/arch/riscv/mm/ptdump.c
> > +++ b/arch/riscv/mm/ptdump.c
> > @@ -129,7 +129,6 @@ static struct ptd_mm_info efi_ptd_info = {
> >  /* Page Table Entry */
> >  struct prot_bits {
> >         u64 mask;
> > -       u64 val;
> >         const char *set;
> >         const char *clear;
> >  };
> > @@ -137,47 +136,38 @@ struct prot_bits {
> >  static const struct prot_bits pte_bits[] = {
> >         {
> >                 .mask = _PAGE_SOFT,
> > -               .val = _PAGE_SOFT,
> > -               .set = "RSW",
> > -               .clear = "   ",
> > +               .set = "RSW(%d)",
> > +               .clear = "      ",
> >         }, {
> >                 .mask = _PAGE_DIRTY,
> > -               .val = _PAGE_DIRTY,
> >                 .set = "D",
> >                 .clear = ".",
> >         }, {
> >                 .mask = _PAGE_ACCESSED,
> > -               .val = _PAGE_ACCESSED,
> >                 .set = "A",
> >                 .clear = ".",
> >         }, {
> >                 .mask = _PAGE_GLOBAL,
> > -               .val = _PAGE_GLOBAL,
> >                 .set = "G",
> >                 .clear = ".",
> >         }, {
> >                 .mask = _PAGE_USER,
> > -               .val = _PAGE_USER,
> >                 .set = "U",
> >                 .clear = ".",
> >         }, {
> >                 .mask = _PAGE_EXEC,
> > -               .val = _PAGE_EXEC,
> >                 .set = "X",
> >                 .clear = ".",
> >         }, {
> >                 .mask = _PAGE_WRITE,
> > -               .val = _PAGE_WRITE,
> >                 .set = "W",
> >                 .clear = ".",
> >         }, {
> >                 .mask = _PAGE_READ,
> > -               .val = _PAGE_READ,
> >                 .set = "R",
> >                 .clear = ".",
> >         }, {
> >                 .mask = _PAGE_PRESENT,
> > -               .val = _PAGE_PRESENT,
> >                 .set = "V",
> >                 .clear = ".",
> >         }
> > @@ -208,15 +198,20 @@ static void dump_prot(struct pg_state *st)
> >         unsigned int i;
> >
> >         for (i = 0; i < ARRAY_SIZE(pte_bits); i++) {
> > -               const char *s;
> > -
> > -               if ((st->current_prot & pte_bits[i].mask) == pte_bits[i].val)
> > -                       s = pte_bits[i].set;
> > +               char s[7];
> > +               unsigned long val;
> > +
> > +               val = st->current_prot & pte_bits[i].mask;
> > +               if (val) {
> > +                       if (pte_bits[i].mask == _PAGE_SOFT)
> > +                               sprintf(s, pte_bits[i].set, val >> 8);
> > +                       else
> > +                               sprintf(s, "%s", pte_bits[i].set);
> > +               }
> >                 else
> > -                       s = pte_bits[i].clear;
> > +                       sprintf(s, "%s", pte_bits[i].clear);
> >
> > -               if (s)
> > -                       pt_dump_seq_printf(st->seq, " %s", s);
> > +               pt_dump_seq_printf(st->seq, " %s", s);
> >         }
> >  }
> >
> > --
> > 2.34.1
> >