Messages in this thread | | | Date | Fri, 24 Mar 2023 11:37:05 +0000 | From | Conor Dooley <> | Subject | Re: [PATCH v1 0/2] RISC-V: Fixes for riscv_has_extension[un]likely()'s alternative dependency |
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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?
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