linux-kernel - Re: [PATCH 05/11] riscv: ptdump: Only show N and MT bits when enabled in the kernel

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Message-ID: <20db5f94-5606-473c-9c5c-ebb0e4488090@ghiti.fr>
Date: Tue, 5 Nov 2024 11:06:36 +0100
From: Alexandre Ghiti <alex@...ti.fr>
To: Samuel Holland <samuel.holland@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, linux-riscv@...ts.infradead.org,
 Conor Dooley <conor@...nel.org>
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 Alexandre Ghiti <alexghiti@...osinc.com>,
 Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
 Emil Renner Berthing <kernel@...il.dk>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>
Subject: Re: [PATCH 05/11] riscv: ptdump: Only show N and MT bits when enabled
 in the kernel

On 02/11/2024 01:07, Samuel Holland wrote:
> When the Svnapot or Svpbmt extension is not implemented, the
> corresponding page table bits are reserved, and must be zero. There is
> no need to show them in the ptdump output.
>
> When the Kconfig option for an extension is disabled, we assume it is
> not implemented. In that case, the kernel may provide a fallback
> definition for the fields, like how _PAGE_MTMASK is defined on riscv32.
> Using those fallback definitions in ptdump would produce incorrect
> results. To avoid this, hide the fields from the ptdump output.
>
> Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
> ---
>
>   arch/riscv/mm/ptdump.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/mm/ptdump.c b/arch/riscv/mm/ptdump.c
> index 9d5f657a251b..58a7322e9a82 100644
> --- a/arch/riscv/mm/ptdump.c
> +++ b/arch/riscv/mm/ptdump.c
> @@ -135,11 +135,13 @@ struct prot_bits {
>   
>   static const struct prot_bits pte_bits[] = {
>   	{
> -#ifdef CONFIG_64BIT
> +#ifdef CONFIG_RISCV_ISA_SVNAPOT
>   		.mask = _PAGE_NAPOT,
>   		.set = "N",
>   		.clear = ".",
>   	}, {
> +#endif
> +#ifdef CONFIG_RISCV_ISA_SVPBMT
>   		.mask = _PAGE_MTMASK_SVPBMT,
>   		.set = "MT(%s)",
>   		.clear = "  ..  ",
> @@ -215,7 +217,7 @@ static void dump_prot(struct pg_state *st)
>   		if (val) {
>   			if (pte_bits[i].mask == _PAGE_SOFT)
>   				sprintf(s, pte_bits[i].set, val >> 8);
> -#ifdef CONFIG_64BIT
> +#ifdef CONFIG_RISCV_ISA_SVPBMT
>   			else if (pte_bits[i].mask == _PAGE_MTMASK_SVPBMT) {
>   				if (val == _PAGE_NOCACHE_SVPBMT)
>   					sprintf(s, pte_bits[i].set, "NC");


It makes sense so:

Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>

Thanks,

Alex