lkml.org 
[lkml]   [2018]   [Jan]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH v2 1/6] arm64: cpufeature: Allow early detect of specific features
    From
    Date


    On 22/01/18 12:05, Suzuki K Poulose wrote:
    > 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 ?
    >

    I see, however I'm not sure what happens in the GIC drivers if we have a
    CPU running with a GICv3 and other CPUs with something else... But of
    course this is not technically limited by the arm64 capabilities handling.

    What behaviour would you be looking for? A way to prevent the CPU to be
    brought up instead of panicking?

    > 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.

    Thanks,

    --
    Julien Thierry

    \
     
     \ /
      Last update: 2018-01-22 13:23    [W:2.086 / U:0.316 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site