Re: [Qemu-devel] [SeaBIOS PATCH 2/2] allow CPUs to have non-contiguous Local APIC IDs (v2)

[Gleb Natapov <gleb@redhat.com>]

On Fri, Jul 20, 2012 at 02:04:50PM -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 not depend
> on any other kind of "CPU identifier". This way, SeaBIOS may change the
> way ACPI Processor IDs are chosen in the future.
> 
> As currently SeaBIOS supports 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 (but this is an internal implementation detail,
> not visible to the OS or on any hardware<=>SeaBIOS interface).
> 
> For current QEMU versions (that always make the APIC IDs contiguous),
> the OS-visible behavior and resulting ACPI tables should be exactly the
> same. This patch will simply allow QEMU to start setting non-contiguous
> APIC IDs (that is a requirement for some sockets/cores/threads topology
> settings).
> 
> Changes v1 -> v2:
>  - Use size suffixes on all asm instructions on smp.c
>  - New patch description
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  src/acpi-dsdt.dsl |    4 +++-
>  src/acpi.c        |    9 +++++----
>  src/mptable.c     |    2 +-
>  src/smp.c         |   17 +++++++++++++++++
>  src/util.h        |    1 +
>  5 files changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/src/acpi-dsdt.dsl b/src/acpi-dsdt.dsl
> index 2060686..72dc7d8 100644
> --- a/src/acpi-dsdt.dsl
> +++ b/src/acpi-dsdt.dsl
> @@ -676,6 +676,7 @@ DefinitionBlock (
>          /* Methods called by run-time generated SSDT Processor objects */
>          Method (CPMA, 1, NotSerialized) {
>              // _MAT method - create an madt apic buffer
> +            // Arg0 = Processor ID = Local APIC ID
>              // Local0 = CPON flag for this cpu
>              Store(DerefOf(Index(CPON, Arg0)), Local0)
>              // Local1 = Buffer (in madt apic form) to return
> @@ -688,6 +689,7 @@ DefinitionBlock (
>          }
>          Method (CPST, 1, NotSerialized) {
>              // _STA method - return ON status of cpu
> +            // Arg0 = Processor ID = Local APIC ID
>              // Local0 = CPON flag for this cpu
>              Store(DerefOf(Index(CPON, Arg0)), Local0)
>              If (Local0) { Return(0xF) } Else { Return(0x0) }
> @@ -708,7 +710,7 @@ DefinitionBlock (
>              Store (PRS, Local5)
>              // Local2 = last read byte from bitmap
>              Store (Zero, Local2)
> -            // Local0 = cpuid iterator
> +            // Local0 = Processor ID / APIC ID iterator
>              Store (Zero, Local0)
>              While (LLess(Local0, SizeOf(CPON))) {
>                  // Local1 = CPON flag for this cpu
> diff --git a/src/acpi.c b/src/acpi.c
> index da3bc57..39b7172 100644
> --- a/src/acpi.c
> +++ b/src/acpi.c
> @@ -327,7 +327,7 @@ build_madt(void)
>          apic->length = sizeof(*apic);
>          apic->processor_id = i;
>          apic->local_apic_id = i;
> -        if (i < CountCPUs)
> +        if (apic_id_is_present(apic->local_apic_id))
>              apic->flags = cpu_to_le32(1);
>          else
>              apic->flags = cpu_to_le32(0);
> @@ -445,6 +445,7 @@ build_ssdt(void)
>      }
>  
>      // build "Method(NTFY, 2) {If (LEqual(Arg0, 0x00)) {Notify(CP00, Arg1)} ...}"
> +    // Arg0 = Processor ID = APIC ID
>      *(ssdt_ptr++) = 0x14; // MethodOp
>      ssdt_ptr = encodeLen(ssdt_ptr, 2+5+(12*acpi_cpus), 2);
>      *(ssdt_ptr++) = 'N';
> @@ -477,7 +478,7 @@ build_ssdt(void)
>      ssdt_ptr = encodeLen(ssdt_ptr, 2+1+(1*acpi_cpus), 2);
>      *(ssdt_ptr++) = acpi_cpus;
>      for (i=0; i<acpi_cpus; i++)
> -        *(ssdt_ptr++) = (i < CountCPUs) ? 0x01 : 0x00;
> +        *(ssdt_ptr++) = (apic_id_is_present(i)) ? 0x01 : 0x00;
>  
>      // store pci io windows: start, end, length
>      // this way we don't have to do the math in the dsdt
> @@ -656,10 +657,10 @@ build_srat(void)
>          core->proximity_lo = curnode;
>          memset(core->proximity_hi, 0, 3);
>          core->local_sapic_eid = 0;
> -        if (i < CountCPUs)
> +        if (apic_id_is_present(i))
>              core->flags = cpu_to_le32(1);
>          else
> -            core->flags = 0;
> +            core->flags = cpu_to_le32(0);
>          core++;
>      }
>  
> diff --git a/src/mptable.c b/src/mptable.c
> index 103f462..9406f98 100644
> --- a/src/mptable.c
> +++ b/src/mptable.c
> @@ -59,7 +59,7 @@ mptable_init(void)
>          cpu->apicid = i;
>          cpu->apicver = apic_version;
>          /* cpu flags: enabled, bootstrap cpu */
> -        cpu->cpuflag = ((i<CountCPUs) ? 0x01 : 0x00) | ((i==0) ? 0x02 : 0x00);
> +        cpu->cpuflag = (apic_id_is_present(i) ? 0x01 : 0x00) | ((i==0) ? 0x02 : 0x00);
>          cpu->cpusignature = cpuid_signature;
>          cpu->featureflag = cpuid_features;
>          cpu++;
> diff --git a/src/smp.c b/src/smp.c
> index 8c077a1..3c36f8c 100644
> --- 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
> +    "  movl $1, %eax\n"
> +    "  cpuid\n"
> +    "  shrl $24, %ebx\n"
> +    "  lock btsl %ebx, FoundAPICIDs\n"
> +
>      // Increment the cpu counter
>      "  lock incl CountCPUs\n"
You can get rid of CountCPUs by calculating FoundAPICIDs bitmap weight.

>  
> @@ -67,6 +75,11 @@ ASM16(
>      "  jmp 1b\n"
>      );
>  
> +int apic_id_is_present(u8 apic_id)
> +{
> +    return FoundAPICIDs[apic_id/32] & (1 << (apic_id % 32));
> +}
> +
>  // find and initialize the CPUs by launching a SIPI to them
>  void
>  smp_probe(void)
> @@ -82,6 +95,10 @@ smp_probe(void)
>          return;
>      }
>  
> +    // mark the BSP initial APIC ID as found, too:
> +    u8 apic_id = ebx>>24;
> +    FoundAPICIDs[apic_id/32] |= (1 << (apic_id % 32));
> +
>      // Init the counter.
>      writel(&CountCPUs, 1);
>  
> diff --git a/src/util.h b/src/util.h
> index ef8ec7c..89e928c 100644
> --- a/src/util.h
> +++ b/src/util.h
> @@ -355,6 +355,7 @@ extern u32 CountCPUs;
>  extern u32 MaxCountCPUs;
>  void wrmsr_smp(u32 index, u64 val);
>  void smp_probe(void);
> +int apic_id_is_present(u8 apic_id);
>  
>  // coreboot.c
>  extern const char *CBvendor, *CBpart;
> -- 
> 1.7.10.4

--
			Gleb.