Re: [PATCH] riscv: correct pt_level name via pgtable_l5/4_enabled

[Palmer Dabbelt]

On Tue, 11 Jul 2023 04:14:10 PDT (-0700), alex@xxxxxxxx wrote:
> Hi Song,
>
>
> On 11/07/2023 12:52, Song Shuai wrote:
> > The pt_level uses CONFIG_PGTABLE_LEVELS to display page table names.
> > But if downgrading page mode from kernel cmdline in 64BIT, it will
> > give a wrong name.
> >
> > Like, using no4lvl for sv39, ptdump named the 1G-mapping as "PUD"
> > that should be "PGD":
> >
> > 0xffffffd840000000-0xffffffd900000000    0x00000000c0000000         3G PUD     D A G . . W R V
> >
> > So select "P4D/PUD" or "PGD" via pgtable_l5/4_enabled to correct it.
> >
> > Fixes: 26e7aacb83df ("riscv: Allow to downgrade paging mode from the command line")
> > Signed-off-by: Song Shuai <suagrfillet@xxxxxxxxx>
> > ---
> >   arch/riscv/mm/ptdump.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/arch/riscv/mm/ptdump.c b/arch/riscv/mm/ptdump.c
> > index 20a9f991a6d7..cfdd327981ee 100644
> > --- a/arch/riscv/mm/ptdump.c
> > +++ b/arch/riscv/mm/ptdump.c
> > @@ -384,6 +384,11 @@ static int __init ptdump_init(void)
> >
> >   	kernel_ptd_info.base_addr = KERN_VIRT_START;
> >
> > +#ifdef CONFIG_64BIT
> > +	pg_level[1].name = pgtable_l5_enabled ? "P4D" : "PGD";
> > +	pg_level[2].name = pgtable_l4_enabled ? "PUD" : "PGD";
> > +#endif
>
>
> You don't need the #ifdef here as pgtable_lX_enabled are always declared.
>
>
> > +
> >   	for (i = 0; i < ARRAY_SIZE(pg_level); i++)
> >   		for (j = 0; j < ARRAY_SIZE(pte_bits); j++)
> >   			pg_level[i].mask |= pte_bits[j].mask;
>
>
> The Fixes tag is wrong to me, if satp mode is restricted by the hardware
> itself (not from the command line), the same problem happens. Maybe that
> should be the sv48 introduction patch? Or the sv57? It will be more
> cumbersome to backport with the sv48 introduction though as this patch
> won't apply as-is.

Sometimes it's easier to base the fix on the original offending commit 
and then forward-port it via a merge, I haven't looked at this one to 
know for sure though.

> Otherwise, you can add:
>
> Reviewed-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>

Thanks.

Song: do you have a v2 that addresses the comments?

> Thanks,
>
> Alex