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Re: [Xen-devel] [PATCH v2 10/15] xen/arm: Detect silicon revision and set cap bits accordingly



On Mon, 23 May 2016, Julien Grall wrote:
> After each CPU has been started, we iterate through a list of CPU
> errata to detect CPUs which need from hypervisor code patches.
> 
> For each bug there is a function which check if that a particular CPU is
> affected. This needs to be done on every CPUs to cover heterogenous
> system properly.
> 
> If a certain erratum has been detected, the capability bit will be set
> and later the call to apply_alternatives() will trigger the actual code
> patching.
> 
> The code is based on the file arch/arm64/kernel/cpu_errata.c in Linux
> v4.6-rc3.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> 
> ---
>     Changes in v2:
>         - Use XENLOG_INFO for the loglevel of the message
> ---
>  xen/arch/arm/Makefile            |  1 +
>  xen/arch/arm/cpuerrata.c         | 26 ++++++++++++++++++++++++++
>  xen/arch/arm/cpufeature.c        | 16 ++++++++++++++++
>  xen/arch/arm/setup.c             |  3 +++
>  xen/arch/arm/smpboot.c           |  3 +++
>  xen/include/asm-arm/cpuerrata.h  |  6 ++++++
>  xen/include/asm-arm/cpufeature.h | 15 +++++++++++++++
>  7 files changed, 70 insertions(+)
>  create mode 100644 xen/arch/arm/cpuerrata.c
>  create mode 100644 xen/include/asm-arm/cpuerrata.h
> 
> diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
> index 2d330aa..307578c 100644
> --- a/xen/arch/arm/Makefile
> +++ b/xen/arch/arm/Makefile
> @@ -7,6 +7,7 @@ subdir-$(CONFIG_ACPI) += acpi
>  obj-$(CONFIG_ALTERNATIVE) += alternative.o
>  obj-y += bootfdt.o
>  obj-y += cpu.o
> +obj-y += cpuerrata.o
>  obj-y += cpufeature.o
>  obj-y += decode.o
>  obj-y += device.o
> diff --git a/xen/arch/arm/cpuerrata.c b/xen/arch/arm/cpuerrata.c
> new file mode 100644
> index 0000000..52d39f8
> --- /dev/null
> +++ b/xen/arch/arm/cpuerrata.c
> @@ -0,0 +1,26 @@
> +#include <xen/config.h>
> +#include <asm/cpufeature.h>
> +#include <asm/cpuerrata.h>
> +
> +#define MIDR_RANGE(model, min, max)     \
> +    .matches = is_affected_midr_range,  \
> +    .midr_model = model,                \
> +    .midr_range_min = min,              \
> +    .midr_range_max = max
> +
> +static bool_t __maybe_unused

I would remove __maybe_unused given that you are going to use this
function in later patches.


> +is_affected_midr_range(const struct arm_cpu_capabilities *entry)
> +{
> +    return MIDR_IS_CPU_MODEL_RANGE(boot_cpu_data.midr.bits, 
> entry->midr_model,
> +                                   entry->midr_range_min,
> +                                   entry->midr_range_max);
> +}
> +
> +static const struct arm_cpu_capabilities arm_errata[] = {
> +    {},
> +};
> +
> +void check_local_cpu_errata(void)
> +{
> +    update_cpu_capabilities(arm_errata, "enabled workaround for");
> +}

update_cpu_capabilities should actually be called on arm64 only, right?
Given that runtime patching is unimplemented on arm32. I wouldn't want
to rely on the fact that we don't have any arm32 workarounds at the
moment.


> diff --git a/xen/arch/arm/cpufeature.c b/xen/arch/arm/cpufeature.c
> index 7a1b56b..088625b 100644
> --- a/xen/arch/arm/cpufeature.c
> +++ b/xen/arch/arm/cpufeature.c
> @@ -24,6 +24,22 @@
>  
>  DECLARE_BITMAP(cpu_hwcaps, ARM_NCAPS);
>  
> +void update_cpu_capabilities(const struct arm_cpu_capabilities *caps,
> +                             const char *info)

The info parameter is unnecessary.


> +{
> +    int i;
> +
> +    for ( i = 0; caps[i].matches; i++ )
> +    {
> +        if ( !caps[i].matches(&caps[i]) )
> +            continue;
> +
> +        if ( !cpus_have_cap(caps[i].capability) && caps[i].desc )
> +            printk(XENLOG_INFO "%s: %s\n", info, caps[i].desc);
> +        cpus_set_cap(caps[i].capability);
> +    }
> +}
> +
>  /*
>   * Local variables:
>   * mode: C
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index c4389ef..67eb13b 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -43,6 +43,7 @@
>  #include <asm/current.h>
>  #include <asm/setup.h>
>  #include <asm/gic.h>
> +#include <asm/cpuerrata.h>
>  #include <asm/cpufeature.h>
>  #include <asm/platform.h>
>  #include <asm/procinfo.h>
> @@ -171,6 +172,8 @@ static void __init processor_id(void)
>      }
>  
>      processor_setup();
> +
> +    check_local_cpu_errata();
>  }
>  
>  void dt_unreserved_regions(paddr_t s, paddr_t e,
> diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
> index c5109bf..3f5a77b 100644
> --- a/xen/arch/arm/smpboot.c
> +++ b/xen/arch/arm/smpboot.c
> @@ -29,6 +29,7 @@
>  #include <xen/timer.h>
>  #include <xen/irq.h>
>  #include <xen/console.h>
> +#include <asm/cpuerrata.h>
>  #include <asm/gic.h>
>  #include <asm/psci.h>
>  #include <asm/acpi.h>
> @@ -316,6 +317,8 @@ void start_secondary(unsigned long boot_phys_offset,
>      local_irq_enable();
>      local_abort_enable();
>  
> +    check_local_cpu_errata();
> +
>      printk(XENLOG_DEBUG "CPU %u booted.\n", smp_processor_id());
>  
>      startup_cpu_idle_loop();
> diff --git a/xen/include/asm-arm/cpuerrata.h b/xen/include/asm-arm/cpuerrata.h
> new file mode 100644
> index 0000000..8ffd7ba
> --- /dev/null
> +++ b/xen/include/asm-arm/cpuerrata.h
> @@ -0,0 +1,6 @@
> +#ifndef __ARM_CPUERRATA_H
> +#define __ARM_CPUERRATA_H
> +
> +void check_local_cpu_errata(void);
> +
> +#endif /* __ARM_CPUERRATA_H */
> diff --git a/xen/include/asm-arm/cpufeature.h 
> b/xen/include/asm-arm/cpufeature.h
> index 2bebad1..fb57295 100644
> --- a/xen/include/asm-arm/cpufeature.h
> +++ b/xen/include/asm-arm/cpufeature.h
> @@ -62,6 +62,21 @@ static inline void cpus_set_cap(unsigned int num)
>          __set_bit(num, cpu_hwcaps);
>  }
>  
> +struct arm_cpu_capabilities {
> +    const char *desc;
> +    u16 capability;
> +    bool_t (*matches)(const struct arm_cpu_capabilities *);
> +    union {
> +        struct {    /* To be used for eratum handling only */
> +            u32 midr_model;
> +            u32 midr_range_min, midr_range_max;
> +        };
> +    };
> +};
> +
> +void update_cpu_capabilities(const struct arm_cpu_capabilities *caps,
> +                             const char *info);
> +
>  #endif /* __ASSEMBLY__ */
>  
>  #endif
> -- 
> 1.9.1
> 

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