arch/riscv/Kconfig | 12 ++++---- arch/riscv/Kconfig.erratas | 6 ++-- arch/riscv/include/asm/hwcap.h | 50 ++++++++++++++++++++-------------- 3 files changed, 38 insertions(+), 30 deletions(-)
Here's my attempt at fixing both the use of an FPU on XIP kernels and
the issue that Jason ran into where CONFIG_FPU, which needs the
alternatives frame work for has_fpu() checks, could be enabled without
the alternatives actually being present.
For the former, a "slow" fallback that does not use alternatives is
added to riscv_has_extension_[un]likely() that can be used with XIP.
Obviously, we want to make use of Jisheng's alternatives based approach
where possible, so any users of riscv_has_extension_[un]likely() will
want to make sure that they select RISCV_ALTERNATIVE.
If they don't however, they'll hit the fallback path which (should,
sparing a silly mistake from me!) behave in the same way, thus
succeeding silently. Sounds like a
To prevent "depends on !XIP_KERNEL; select RISCV_ALTERNATIVE" spreading
like the plague through the various places that want to check for the
presence of extensions, and sidestep the potential silent "success"
mentioned above, all users RISCV_ALTERNATIVE are converted from selects
to dependencies, with the option being selected for all !XIP_KERNEL
builds.
I know that the VDSO was a key place that Jisheng wanted to use the new
helper rather than static branches, and I think the fallback path
should not cause issues there.
See the thread at [1] for the prior discussion.
Cheers,
Conor.
1 - https://lore.kernel.org/linux-riscv/20230128172856.3814-1-jszhang@kernel.org/T/#m21390d570997145d31dd8bb95002fd61f99c6573
CC: Paul Walmsley <paul.walmsley@sifive.com>
CC: Palmer Dabbelt <palmer@dabbelt.com>
CC: Conor Dooley <conor.dooley@microchip.com>
CC: Heiko Stuebner <heiko.stuebner@vrull.eu>
CC: Andrew Jones <ajones@ventanamicro.com>
CC: Anup Patel <apatel@ventanamicro.com>
CC: Jisheng Zhang <jszhang@kernel.org>
CC: Andrew Jones <ajones@ventanamicro.com>
CC: Jason A. Donenfeld <Jason@zx2c4.com>
CC: linux-riscv@lists.infradead.org
CC: linux-kernel@vger.kernel.org
Conor Dooley (2):
RISC-V: add non-alternative fallback for
riscv_has_extension_[un]likely()
RISC-V: always select RISCV_ALTERNATIVE for non-xip kernels
arch/riscv/Kconfig | 12 ++++----
arch/riscv/Kconfig.erratas | 6 ++--
arch/riscv/include/asm/hwcap.h | 50 ++++++++++++++++++++--------------
3 files changed, 38 insertions(+), 30 deletions(-)
--
2.39.2
Hello:
This series was applied to riscv/linux.git (fixes)
by Palmer Dabbelt <palmer@rivosinc.com>:
On Fri, 24 Mar 2023 10:05:37 +0000 you wrote:
> Here's my attempt at fixing both the use of an FPU on XIP kernels and
> the issue that Jason ran into where CONFIG_FPU, which needs the
> alternatives frame work for has_fpu() checks, could be enabled without
> the alternatives actually being present.
>
> For the former, a "slow" fallback that does not use alternatives is
> added to riscv_has_extension_[un]likely() that can be used with XIP.
> Obviously, we want to make use of Jisheng's alternatives based approach
> where possible, so any users of riscv_has_extension_[un]likely() will
> want to make sure that they select RISCV_ALTERNATIVE.
> If they don't however, they'll hit the fallback path which (should,
> sparing a silly mistake from me!) behave in the same way, thus
> succeeding silently. Sounds like a
>
> [...]
Here is the summary with links:
- [v1,1/2] RISC-V: add non-alternative fallback for riscv_has_extension_[un]likely()
https://git.kernel.org/riscv/c/1aa866931b80
- [v1,2/2] RISC-V: always select RISCV_ALTERNATIVE for non-xip kernels
https://git.kernel.org/riscv/c/1ee7fc3f4d0a
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
On Fri, 24 Mar 2023 10:05:37 +0000, Conor Dooley wrote:
> Here's my attempt at fixing both the use of an FPU on XIP kernels and
> the issue that Jason ran into where CONFIG_FPU, which needs the
> alternatives frame work for has_fpu() checks, could be enabled without
> the alternatives actually being present.
>
> For the former, a "slow" fallback that does not use alternatives is
> added to riscv_has_extension_[un]likely() that can be used with XIP.
> Obviously, we want to make use of Jisheng's alternatives based approach
> where possible, so any users of riscv_has_extension_[un]likely() will
> want to make sure that they select RISCV_ALTERNATIVE.
> If they don't however, they'll hit the fallback path which (should,
> sparing a silly mistake from me!) behave in the same way, thus
> succeeding silently. Sounds like a
>
> [...]
Applied, thanks!
[1/2] RISC-V: add non-alternative fallback for riscv_has_extension_[un]likely()
https://git.kernel.org/palmer/c/1aa866931b80
[2/2] RISC-V: always select RISCV_ALTERNATIVE for non-xip kernels
https://git.kernel.org/palmer/c/1ee7fc3f4d0a
Best regards,
--
Palmer Dabbelt <palmer@rivosinc.com>
Seems like a good approach to me. I'm not a RISC-V maintainer or reviewer, but in case it helps, Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
On Fri, Mar 24, 2023 at 10:05:37AM +0000, Conor Dooley wrote: > Here's my attempt at fixing both the use of an FPU on XIP kernels and > the issue that Jason ran into where CONFIG_FPU, which needs the > alternatives frame work for has_fpu() checks, could be enabled without > the alternatives actually being present. > > For the former, a "slow" fallback that does not use alternatives is > added to riscv_has_extension_[un]likely() that can be used with XIP. > Obviously, we want to make use of Jisheng's alternatives based approach > where possible, so any users of riscv_has_extension_[un]likely() will > want to make sure that they select RISCV_ALTERNATIVE. > If they don't however, they'll hit the fallback path which (should, > sparing a silly mistake from me!) behave in the same way, thus > succeeding silently. Sounds like a > > To prevent "depends on !XIP_KERNEL; select RISCV_ALTERNATIVE" spreading > like the plague through the various places that want to check for the > presence of extensions, and sidestep the potential silent "success" > mentioned above, all users RISCV_ALTERNATIVE are converted from selects > to dependencies, with the option being selected for all !XIP_KERNEL > builds. > > I know that the VDSO was a key place that Jisheng wanted to use the new > helper rather than static branches, and I think the fallback path > should not cause issues there. > > See the thread at [1] for the prior discussion. > > Cheers, > Conor. > > 1 - https://lore.kernel.org/linux-riscv/20230128172856.3814-1-jszhang@kernel.org/T/#m21390d570997145d31dd8bb95002fd61f99c6573 > > CC: Paul Walmsley <paul.walmsley@sifive.com> > CC: Palmer Dabbelt <palmer@dabbelt.com> > CC: Conor Dooley <conor.dooley@microchip.com> > CC: Heiko Stuebner <heiko.stuebner@vrull.eu> > CC: Andrew Jones <ajones@ventanamicro.com> > CC: Anup Patel <apatel@ventanamicro.com> > CC: Jisheng Zhang <jszhang@kernel.org> > CC: Andrew Jones <ajones@ventanamicro.com> > CC: Jason A. Donenfeld <Jason@zx2c4.com> > CC: linux-riscv@lists.infradead.org > CC: linux-kernel@vger.kernel.org > > Conor Dooley (2): > RISC-V: add non-alternative fallback for > riscv_has_extension_[un]likely() > RISC-V: always select RISCV_ALTERNATIVE for non-xip kernels > > arch/riscv/Kconfig | 12 ++++---- > arch/riscv/Kconfig.erratas | 6 ++-- > arch/riscv/include/asm/hwcap.h | 50 ++++++++++++++++++++-------------- > 3 files changed, 38 insertions(+), 30 deletions(-) > > -- > 2.39.2 > LGTM, but if it was based on for-next then it could also immediately be applied to zicboz. For the series, Reviewed-by: Andrew Jones <ajones@ventanamicro.com> Thanks, drew
On Fri, Mar 24, 2023 at 12:31:07PM +0100, Andrew Jones wrote: > On Fri, Mar 24, 2023 at 10:05:37AM +0000, Conor Dooley wrote: > > Here's my attempt at fixing both the use of an FPU on XIP kernels and > > the issue that Jason ran into where CONFIG_FPU, which needs the > > alternatives frame work for has_fpu() checks, could be enabled without > > the alternatives actually being present. > > > > For the former, a "slow" fallback that does not use alternatives is > > added to riscv_has_extension_[un]likely() that can be used with XIP. > > Obviously, we want to make use of Jisheng's alternatives based approach > > where possible, so any users of riscv_has_extension_[un]likely() will > > want to make sure that they select RISCV_ALTERNATIVE. > > If they don't however, they'll hit the fallback path which (should, > > sparing a silly mistake from me!) behave in the same way, thus > > succeeding silently. Sounds like a > > > > To prevent "depends on !XIP_KERNEL; select RISCV_ALTERNATIVE" spreading > > like the plague through the various places that want to check for the > > presence of extensions, and sidestep the potential silent "success" > > mentioned above, all users RISCV_ALTERNATIVE are converted from selects > > to dependencies, with the option being selected for all !XIP_KERNEL > > builds. > > > > I know that the VDSO was a key place that Jisheng wanted to use the new > > helper rather than static branches, and I think the fallback path > > should not cause issues there. > > > > See the thread at [1] for the prior discussion. > > > > Cheers, > > Conor. > > > > 1 - https://lore.kernel.org/linux-riscv/20230128172856.3814-1-jszhang@kernel.org/T/#m21390d570997145d31dd8bb95002fd61f99c6573 > > > > CC: Paul Walmsley <paul.walmsley@sifive.com> > > CC: Palmer Dabbelt <palmer@dabbelt.com> > > CC: Conor Dooley <conor.dooley@microchip.com> > > CC: Heiko Stuebner <heiko.stuebner@vrull.eu> > > CC: Andrew Jones <ajones@ventanamicro.com> > > CC: Anup Patel <apatel@ventanamicro.com> > > CC: Jisheng Zhang <jszhang@kernel.org> > > CC: Andrew Jones <ajones@ventanamicro.com> > > CC: Jason A. Donenfeld <Jason@zx2c4.com> > > CC: linux-riscv@lists.infradead.org > > CC: linux-kernel@vger.kernel.org > > > > Conor Dooley (2): > > RISC-V: add non-alternative fallback for > > riscv_has_extension_[un]likely() > > RISC-V: always select RISCV_ALTERNATIVE for non-xip kernels > > > > arch/riscv/Kconfig | 12 ++++---- > > arch/riscv/Kconfig.erratas | 6 ++-- > > arch/riscv/include/asm/hwcap.h | 50 ++++++++++++++++++++-------------- > > 3 files changed, 38 insertions(+), 30 deletions(-) > > > > -- > > 2.39.2 > > > > LGTM, but if it was based on for-next then it could also immediately be > applied to zicboz. For the series, Hmm, I did it on top of fixes since this needs to go into v6.3. Perhaps I can create a standalone patch for Zicboz and Palmer could merge these two into both fixes & for-next, with the standalone applied on top?
On Fri, Mar 24, 2023 at 11:37:05AM +0000, Conor Dooley wrote: > On Fri, Mar 24, 2023 at 12:31:07PM +0100, Andrew Jones wrote: > > On Fri, Mar 24, 2023 at 10:05:37AM +0000, Conor Dooley wrote: > > > Here's my attempt at fixing both the use of an FPU on XIP kernels and > > > the issue that Jason ran into where CONFIG_FPU, which needs the > > > alternatives frame work for has_fpu() checks, could be enabled without > > > the alternatives actually being present. > > > > > > For the former, a "slow" fallback that does not use alternatives is > > > added to riscv_has_extension_[un]likely() that can be used with XIP. > > > Obviously, we want to make use of Jisheng's alternatives based approach > > > where possible, so any users of riscv_has_extension_[un]likely() will > > > want to make sure that they select RISCV_ALTERNATIVE. > > > If they don't however, they'll hit the fallback path which (should, > > > sparing a silly mistake from me!) behave in the same way, thus > > > succeeding silently. Sounds like a > > > > > > To prevent "depends on !XIP_KERNEL; select RISCV_ALTERNATIVE" spreading > > > like the plague through the various places that want to check for the > > > presence of extensions, and sidestep the potential silent "success" > > > mentioned above, all users RISCV_ALTERNATIVE are converted from selects > > > to dependencies, with the option being selected for all !XIP_KERNEL > > > builds. > > > > > > I know that the VDSO was a key place that Jisheng wanted to use the new > > > helper rather than static branches, and I think the fallback path > > > should not cause issues there. > > > > > > See the thread at [1] for the prior discussion. > > > > > > Cheers, > > > Conor. > > > > > > 1 - https://lore.kernel.org/linux-riscv/20230128172856.3814-1-jszhang@kernel.org/T/#m21390d570997145d31dd8bb95002fd61f99c6573 > > > > > > CC: Paul Walmsley <paul.walmsley@sifive.com> > > > CC: Palmer Dabbelt <palmer@dabbelt.com> > > > CC: Conor Dooley <conor.dooley@microchip.com> > > > CC: Heiko Stuebner <heiko.stuebner@vrull.eu> > > > CC: Andrew Jones <ajones@ventanamicro.com> > > > CC: Anup Patel <apatel@ventanamicro.com> > > > CC: Jisheng Zhang <jszhang@kernel.org> > > > CC: Andrew Jones <ajones@ventanamicro.com> > > > CC: Jason A. Donenfeld <Jason@zx2c4.com> > > > CC: linux-riscv@lists.infradead.org > > > CC: linux-kernel@vger.kernel.org > > > > > > Conor Dooley (2): > > > RISC-V: add non-alternative fallback for > > > riscv_has_extension_[un]likely() > > > RISC-V: always select RISCV_ALTERNATIVE for non-xip kernels > > > > > > arch/riscv/Kconfig | 12 ++++---- > > > arch/riscv/Kconfig.erratas | 6 ++-- > > > arch/riscv/include/asm/hwcap.h | 50 ++++++++++++++++++++-------------- > > > 3 files changed, 38 insertions(+), 30 deletions(-) > > > > > > -- > > > 2.39.2 > > > > > > > LGTM, but if it was based on for-next then it could also immediately be > > applied to zicboz. For the series, > > Hmm, I did it on top of fixes since this needs to go into v6.3. Ah, sure. > Perhaps I can create a standalone patch for Zicboz and Palmer could merge > these two into both fixes & for-next, with the standalone applied on > top? Sounds good. Thanks, drew
© 2016 - 2026 Red Hat, Inc.