Re: [Xen-devel] [for-4.7 2/5] xen/arm: acpi: The boot CPU does not always match the first entry in the MADT

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 7 Apr 2016, Julien Grall wrote:
> Since the ACPI 6.0 errata document [1], the first entry in the MADT
> does not have to correspond to the boot CPU.
> 
> Introduce a new variable to know if a MADT entry matching the boot CPU
> is found. Furthermore, it's not necessary to check if the MPIDR is
> duplicated for the boot CPU. So the rest of the function can be skipped.
> 
> [1] 1380 Unnecessary restrictions to FW vendors in ordering of GIC structures
> in MADT
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> ---
>  xen/arch/arm/acpi/boot.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/arm/acpi/boot.c b/xen/arch/arm/acpi/boot.c
> index 859aa86..2a71660 100644
> --- a/xen/arch/arm/acpi/boot.c
> +++ b/xen/arch/arm/acpi/boot.c
> @@ -37,7 +37,8 @@
>  #include <asm/setup.h>
>  
>  /* Processors with enabled flag and sane MPIDR */
> -static unsigned int enabled_cpus;
> +static unsigned int enabled_cpus = 1;
> +static bool __initdata bootcpu_valid;
>  
>  /* total number of cpus in this system */
>  static unsigned int __initdata total_cpus;
> @@ -71,10 +72,15 @@ acpi_map_gic_cpu_interface(struct 
> acpi_madt_generic_interrupt *processor)
>      }
>  
>      /* Check if GICC structure of boot CPU is available in the MADT */
> -    if ( (enabled_cpus == 0) && (cpu_logical_map(0) != mpidr) )
> +    if ( cpu_logical_map(0) == mpidr )
>      {
> -        printk("Firmware bug, invalid CPU MPIDR for cpu0: 0x%"PRIx64" in 
> MADT\n",
> -               mpidr);
> +        if ( bootcpu_valid )
> +        {
> +            printk("Firmware bug, duplicate boot CPU MPIDR: 0x%"PRIx64" in 
> MADT\n",
> +                   mpidr);
> +            return;
> +        }
> +        bootcpu_valid = true;
>          return;
>      }

In that case you can start the other loop below from i = 1, instead of
i = 0.

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