Received-SPF: pass (google.com: domain of linux-kernel+bounces-170813-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
Date: Tue, 07 May 2024 08:25:09 +0100
From: Conor Dooley <conor@kernel.org>
To: Charlie Jenkins <charlie@rivosinc.com>,
 Paul Walmsley <paul.walmsley@sifive.com>,
 Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>,
 Conor Dooley <conor.dooley@microchip.com>, Song Liu <song@kernel.org>,
 Xi Wang <xi.wang@gmail.com>,
 =?ISO-8859-1?Q?Bj=F6rn_T=F6pel?= <bjorn@rivosinc.com>,
 =?ISO-8859-1?Q?Cl=E9ment_L=E9ger?= <cleger@rivosinc.com>
CC: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/8] riscv: Support compiling the kernel with extensions
User-Agent: K-9 Mail for Android
In-Reply-To: <20240506-compile_kernel_with_extensions-v1-0-5c25c134c097@rivosinc.com>
References: <20240506-compile_kernel_with_extensions-v1-0-5c25c134c097@rivosinc.com>
Message-ID: <12808AB2-0308-4013-9624-E3DEFCC584EA@kernel.org>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain;
 charset=utf-8
Content-Transfer-Encoding: quoted-printable

Hey Charlie,

On 7 May 2024 02:40:41 IST, Charlie Jenkins <charlie@rivosinc=2Ecom> wrote=
:
>The kernel currently has the restriction that it can only be compiled
>with the extensions that are hardcoded in arch/risc/Makefile=2E
>
>Any extension that is not listed in the Makefile can still be used by
>explicitly writing the assembly and using alternative patching=2E
>
>This series introduces Kconfig options that allow the kernel to be
>compiled with additional extensions=2E

One thing I don't see in the commit messages or the cover letter is what y=
our actual motivation is
for making these changes=2E
Are you effectively looking to evaluate the alternatives at build time, or=
 are you looking to
let the compiler use the extension where it sees
fit? Or perhaps both?

Thanks,
Conor=2E

>
>Signed-off-by: Charlie Jenkins <charlie@rivosinc=2Ecom>
>---
>Charlie Jenkins (8):
>      riscv: Add PLATFORM_MAY_SUPPORT_RISCV_ISA_C Kconfig option
>      riscv: Add PLATFORM_MAY_SUPPORT_RISCV_ISA_V Kconfig option
>      riscv: Add PLATFORM_SUPPORTS_RISCV_ISA_SVNAPOT Kconfig option
>      riscv: Add PLATFORM_MAY_SUPPORT_RISCV_ISA_SVPBMT Kconfig option
>      riscv: Add PLATFORM_SUPPORTS_RISCV_ISA_ZBB Kconfig option
>      riscv: Add PLATFORM_SUPPORTS_RISCV_ISA_ZBA Kconfig option
>      riscv: Add PLATFORM_SUPPORTS_RISCV_ISA_ZBC Kconfig option
>      riscv: Add PLATFORM_SUPPORTS_RISCV_ISA_ZBS Kconfig option
>
> arch/riscv/Kconfig                    | 135 +-----------
> arch/riscv/Kconfig=2Eisa                | 393 ++++++++++++++++++++++++++=
++++++++
> arch/riscv/Makefile                   |  15 +-
> arch/riscv/crypto/Kconfig             |  14 +-
> arch/riscv/include/asm/arch_hweight=2Eh |  33 +--
> arch/riscv/include/asm/checksum=2Eh     |  18 +-
> arch/riscv/include/asm/pgtable=2Eh      |   3 +-
> arch/riscv/include/asm/simd=2Eh         |   3 +
> arch/riscv/include/asm/vector=2Eh       |   3 +-
> arch/riscv/kernel/cpufeature=2Ec        |   3 +-
> arch/riscv/kernel/head=2ES              |   8 +-
> arch/riscv/kernel/probes/uprobes=2Ec    |   2 +-
> arch/riscv/kernel/process=2Ec           |  14 +-
> arch/riscv/kernel/ptrace=2Ec            |   6 +
> arch/riscv/lib/csum=2Ec                 |  48 ++---
> arch/riscv/lib/riscv_v_helpers=2Ec      |   1 -
> arch/riscv/lib/strcmp=2ES               |   4 +-
> arch/riscv/lib/strlen=2ES               |   4 +-
> arch/riscv/lib/strncmp=2ES              |   4 +-
> arch/riscv/lib/uaccess_vector=2ES       |   2 +
> arch/riscv/lib/xor=2ES                  |   2 +
> arch/riscv/net/bpf_jit=2Eh              |   8 +-
> 22 files changed, 511 insertions(+), 212 deletions(-)
>---
>base-commit: 2f47357557b7aa98d9d9002688aae480864ca3f6
>change-id: 20240429-compile_kernel_with_extensions-92dd2403d325