Messages in this thread |  | | Subject | Re: [PATCH v2 1/6] arm64: cpufeature: Allow early detect of specific features | From | Suzuki K Poulose <> | Date | Mon, 22 Jan 2018 12:05:52 +0000 |
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On 17/01/18 11:54, Julien Thierry wrote: > From: Daniel Thompson <daniel.thompson@linaro.org> > > Currently it is not possible to detect features of the boot CPU > until the other CPUs have been brought up. > > This prevents us from reacting to features of the boot CPU until > fairly late in the boot process. To solve this we allow a subset > of features (that are likely to be common to all clusters) to be > detected based on the boot CPU alone. > > Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> > [julien.thierry@arm.com: check non-boot cpu missing early features, avoid > duplicates between early features and normal > features] > Signed-off-by: Julien Thierry <julien.thierry@arm.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Suzuki K Poulose <suzuki.poulose@arm.com> > --- > arch/arm64/kernel/cpufeature.c | 69 ++++++++++++++++++++++++++++-------------- > 1 file changed, 47 insertions(+), 22 deletions(-) > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index a73a592..6698404 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -52,6 +52,8 @@ > DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS); > EXPORT_SYMBOL(cpu_hwcaps); > > +static void __init setup_early_feature_capabilities(void); > + > /* > * Flag to indicate if we have computed the system wide > * capabilities based on the boot time active CPUs. This > @@ -542,6 +544,8 @@ void __init init_cpu_features(struct cpuinfo_arm64 *info) > init_cpu_ftr_reg(SYS_ZCR_EL1, info->reg_zcr); > sve_init_vq_map(); > } > + > + setup_early_feature_capabilities(); > } > > static void update_cpu_ftr_reg(struct arm64_ftr_reg *reg, u64 new) > @@ -846,7 +850,7 @@ static bool has_no_fpsimd(const struct arm64_cpu_capabilities *entry, int __unus > ID_AA64PFR0_FP_SHIFT) < 0; > } > > -static const struct arm64_cpu_capabilities arm64_features[] = { > +static const struct arm64_cpu_capabilities arm64_early_features[] = { > { > .desc = "GIC system register CPU interface", > .capability = ARM64_HAS_SYSREG_GIC_CPUIF, > @@ -857,6 +861,10 @@ static bool has_no_fpsimd(const struct arm64_cpu_capabilities *entry, int __unus > .sign = FTR_UNSIGNED, > .min_field_value = 1, > }, > + {} > +}; > +
Julien,
One potential problem with this is that we don't have a way to make this work on a "theoretical" system with and without GIC system reg interface. i.e, if we don't have the CONFIG enabled for using ICC system regs for IRQ flags, the kernel could still panic. I understand this is not a "normal" configuration but, may be we could make the panic option based on whether we actually use the system regs early enough ?
Btw, I am rewriting the capabilities infrastructure to allow per-cap control on how it should be treated. I might add an EARLY scope for caps which could cover this and may be VHE.
Suzuki
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