Re: [PATCH 2/4] x86/MCE: restrict allocation of thermal and CMCI vector to BSP

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 19/11/2025 10:50 am, Jan Beulich wrote:
> --- a/xen/arch/x86/cpu/mcheck/mce.c
> +++ b/xen/arch/x86/cpu/mcheck/mce.c
> @@ -110,13 +110,13 @@ static void __init mcheck_intel_therm_in
>  }
>  
>  /* P4/Xeon Thermal regulation detect and init */
> -static void intel_init_thermal(struct cpuinfo_x86 *c)
> +static void intel_init_thermal(const struct cpuinfo_x86 *c, bool bsp)
>  {
>      uint64_t msr_content;
>      uint32_t val;
>      int tm2 = 0;
>      unsigned int cpu = smp_processor_id();
> -    static uint8_t thermal_apic_vector;
> +    static uint8_t __ro_after_init thermal_apic_vector;
>  
>      if ( !intel_thermal_supported(c) )
>          return; /* -ENODEV */
> @@ -160,7 +160,8 @@ static void intel_init_thermal(struct cp
>          return; /* -EBUSY */
>      }
>  
> -    alloc_direct_apic_vector(&thermal_apic_vector, intel_thermal_interrupt);
> +    if ( bsp )
> +        alloc_direct_apic_vector(&thermal_apic_vector, 
> intel_thermal_interrupt);

We really don't want both c and bsp passed in.  That can only go wrong.

Furthermore, this function has 2 other examples generating bsp locally.

The function is in desperate need of cleanup (MSRs, variable and
constant names), but right now this makes it worse.

Please either use c == &boot_cpu_data, and I'll do some cleanup later,
or generate bsp = c == &boot_cpu_data and fix up all users in the function.

~Andrew