Re: [Qemu-devel] [SeaBIOS] [seabios PATCH 2/2] allow CPUs to have non-contiguous Local APIC IDs

[Kevin O'Connor <kevin@koconnor.net>]

On Thu, Jul 19, 2012 at 05:52:42PM -0300, Eduardo Habkost wrote:
> Extract Local APIC IDs directly from the CPUs, and instead of check for
> "i < CountCPUs", check if the APIC ID was present on boot, when building
> ACPI tables and the MP-Table.
> 
> This keeps ACPI Processor ID == APIC ID, but allows the
> hardware<->Seabios interface be completely APIC-ID based, and Seabios
> may change the way ACPI Processor IDs are chosen in the future.
> 
> As we currently Seabios support only xAPIC and not x2APIC, the list of
> present-on-boot APIC IDs is a 256-bit bitmap. If one day Seabios starts
> to support x2APIC, the data structure used to enumerate the APIC IDs
> will have to be changed.

Is this SeaBIOS change dependent on a particular version of QEMU?

[...]
> --- a/src/smp.c
> +++ b/src/smp.c
> @@ -36,6 +36,8 @@ wrmsr_smp(u32 index, u64 val)
>  
>  u32 CountCPUs VAR16VISIBLE;
>  u32 MaxCountCPUs VAR16VISIBLE;
> +// 256 bits for the found APIC IDs
> +u32 FoundAPICIDs[256/32] VAR16VISIBLE;
>  extern void smp_ap_boot_code(void);
>  ASM16(
>      "  .global smp_ap_boot_code\n"
> @@ -59,6 +61,12 @@ ASM16(
>      "  jmp 1b\n"
>      "2:\n"
>  
> +    // get apic ID on EBX, set bit on FoundAPICIDs
> +    "  mov $1, %eax\n"
> +    "  cpuid\n"
> +    "  shrl $24, %ebx\n"
> +    "  lock bts %ebx, FoundAPICIDs\n"

Because of the insanity that is 16bit mode, please use explicit size
suffixes on assembler instructions (ie, "movl" and "btsl").

-Kevin