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Subject: Re: [PATCH -fixes] riscv: Check the virtual alignment before choosing
 a map size
From:   Jessica Clarke <jrtc27@jrtc27.com>
In-Reply-To: <20230607125851.63370-1-alexghiti@rivosinc.com>
Date:   Wed, 7 Jun 2023 14:09:28 +0100
Cc:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Andrew Jones <ajones@ventanamicro.com>,
        Rob Herring <robh@kernel.org>,
        Anup Patel <anup@brainfault.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Song Shuai <songshuaishuai@tinylab.org>
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Message-Id: <E8ECB3E5-8DDA-443A-AD00-D337708DBE4C@jrtc27.com>
References: <20230607125851.63370-1-alexghiti@rivosinc.com>
To:     Alexandre Ghiti <alexghiti@rivosinc.com>
Precedence: bulk

On 7 Jun 2023, at 13:58, Alexandre Ghiti <alexghiti@rivosinc.com> wrote:
>=20
> We used to only check the alignment of the physical address to decide
> which mapping would fit for a certain region of the linear mapping, =
but
> it is not enough since the virtual address must also be aligned, so =
check
> that too.
>=20
> Fixes: 3335068f8721 ("riscv: Use PUD/P4D/PGD pages for the linear =
mapping")
> Reported-by: Song Shuai <songshuaishuai@tinylab.org>
> Link: =
https://lore.kernel.org/linux-riscv/tencent_7C3B580B47C1B17C16488EC1@qq.co=
m/
> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> ---
> arch/riscv/mm/init.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>=20
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index d42ea31c7de0..5143eef4c074 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -660,18 +660,19 @@ void __init create_pgd_mapping(pgd_t *pgdp,
> create_pgd_next_mapping(nextp, va, pa, sz, prot);
> }
>=20
> -static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t =
size)
> +static uintptr_t __init best_map_size(phys_addr_t pa, uintptr_t va,

Why on earth is this returning uintptr_t? It=E2=80=99s a size not a =
pointer.

Jess

> +      phys_addr_t size)
> {
> - if (!(base & (PGDIR_SIZE - 1)) && size >=3D PGDIR_SIZE)
> + if (!(pa & (PGDIR_SIZE - 1)) && !(va & (PGDIR_SIZE - 1)) && size >=3D =
PGDIR_SIZE)
> return PGDIR_SIZE;
>=20
> - if (!(base & (P4D_SIZE - 1)) && size >=3D P4D_SIZE)
> + if (!(pa & (P4D_SIZE - 1)) && !(va & (P4D_SIZE - 1)) && size >=3D =
P4D_SIZE)
> return P4D_SIZE;
>=20
> - if (!(base & (PUD_SIZE - 1)) && size >=3D PUD_SIZE)
> + if (!(pa & (PUD_SIZE - 1)) && !(va & (PUD_SIZE - 1)) && size >=3D =
PUD_SIZE)
> return PUD_SIZE;
>=20
> - if (!(base & (PMD_SIZE - 1)) && size >=3D PMD_SIZE)
> + if (!(pa & (PMD_SIZE - 1)) && !(va & (PMD_SIZE - 1)) && size >=3D =
PMD_SIZE)
> return PMD_SIZE;
>=20
> return PAGE_SIZE;
> @@ -1177,7 +1178,7 @@ static void __init =
create_linear_mapping_range(phys_addr_t start,
> for (pa =3D start; pa < end; pa +=3D map_size) {
> va =3D (uintptr_t)__va(pa);
> map_size =3D fixed_map_size ? fixed_map_size :
> -    best_map_size(pa, end - pa);
> +    best_map_size(pa, va, end - pa);
>=20
> create_pgd_mapping(swapper_pg_dir, va, pa, map_size,
>   pgprot_from_va(va));
> --=20
> 2.39.2
>=20
>=20
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