| Message ID | 20230324100538.3514663-1-conor.dooley@microchip.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | RISC-V: Fixes for riscv_has_extension[un]likely()'s alternative dependency | expand |
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
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, 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,
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!
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(-)