Date:   Mon, 23 Jan 2023 14:08:20 +0000
From:   Conor Dooley <conor.dooley@microchip.com>
To:     Alexandre Ghiti <alex@ghiti.fr>
CC:     Alexandre Ghiti <alexghiti@rivosinc.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Conor Dooley <conor@kernel.org>, <linux-doc@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-riscv@lists.infradead.org>,
        =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= <bjorn@kernel.org>
Subject: Re: [PATCH v3] riscv: Allow to downgrade paging mode from the command
Message-ID: <Y86U1OUqlo05Co+2@wendy>
References: <20230123104841.813999-1-alexghiti@rivosinc.com>
 <Y851L2KgfIF3V6of@wendy>
 <95d81c9a-11de-7f92-cb76-e4492e9faba8@ghiti.fr>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha256;
        protocol="application/pgp-signature"; boundary="UiaEVa5YDx4RQv/n"
Content-Disposition: inline
In-Reply-To: <95d81c9a-11de-7f92-cb76-e4492e9faba8@ghiti.fr>
Precedence: bulk

--UiaEVa5YDx4RQv/n
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Mon, Jan 23, 2023 at 02:39:35PM +0100, Alexandre Ghiti wrote:
> Hi Conor,
>=20
> On 1/23/23 12:53, Conor Dooley wrote:
> > Hey Alex,
> >=20
> > On Mon, Jan 23, 2023 at 11:48:41AM +0100, Alexandre Ghiti wrote:
> > > Add 2 early command line parameters that allow to downgrade satp mode
> > > (using the same naming as x86):
> > > - "no5lvl": use a 4-level page table (down from sv57 to sv48)
> > > - "no4lvl": use a 3-level page table (down from sv57/sv48 to sv39)
> > >=20
> > > Note that going through the device tree to get the kernel command line
> > > works with ACPI too since the efi stub creates a device tree anyway w=
ith
> > > the command line.
> > >=20
> > > Also, as those params are treated very early in the boot process and =
we
> > > use standard device tree functions that may be kasan instrumented, we
> > > only enable them for !KASAN configurations.
> > >=20
> > > Reviewed-by: Bj=F6rn T=F6pel <bjorn@kernel.org>
> > > Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> > > ---
> > A changelog would be nice here, especially since this is a resend.
>=20
>=20
> I think you may have commented the wrong patch, this one is wrong, hence =
the
> resend!

Oh, sorry about that Alex! For some reason the resend never landed in my
mailbox (I had just seen that there were two on patchwork).

> > >   .../admin-guide/kernel-parameters.txt         |  9 ++-
> > >   arch/riscv/mm/init.c                          | 72 ++++++++++++++++=
+--
> > >   2 files changed, 74 insertions(+), 7 deletions(-)
> > >=20
> > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Docume=
ntation/admin-guide/kernel-parameters.txt
> > > index 6cfa6e3996cf..fd647412ec91 100644
> > > --- a/Documentation/admin-guide/kernel-parameters.txt
> > > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > > @@ -3578,8 +3578,15 @@
> > >   			emulation library even if a 387 maths coprocessor
> > >   			is present.
> > > -	no5lvl		[X86-64] Disable 5-level paging mode. Forces
> > > +	no4lvl		[RISCV] Disable 4-level and 5-level paging modes. Forces
> > > +			kernel to use 3-level paging instead.
> > > +			Note: On RISC-V, this can't be used when KASAN is
> > > +			enabled.
> > > +
> > > +	no5lvl		[X86-64,RISCV] Disable 5-level paging mode. Forces
> > >   			kernel to use 4-level paging instead.
> > > +			Note: On RISC-V, this can't be used when KASAN is
> > > +			enabled.
> > >   	nofsgsbase	[X86] Disables FSGSBASE instructions.
> > For the improved descriptions & commit message:
> > Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
>=20
>=20
> Thanks for that, would you mind adding that to the resend patch?

Yah, no problem.


--UiaEVa5YDx4RQv/n
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----

iHUEABYIAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCY86U1AAKCRB4tDGHoIJi
0imrAQDr67fpe2CRsNEFP9GsTsQ0z2nPPr0ABLhuiUAxIx7oSQEA7Hc3dTb6PuoN
cjZOoZgwfZCavRbAR0WI1222Xo1v5gE=
=74yN
-----END PGP SIGNATURE-----

--UiaEVa5YDx4RQv/n--