[XS] Change in coreboot[master]: soc/intel/common: Fix invalid MADT entries creation

[Jérémy Compostella (Code Review)]

Attention is currently required from: Arthur Heymans, Jérémy Compostella, Subrata Banik, Sukumar Ghorai, sridhar siricilla.

Hello Arthur Heymans, Subrata Banik, Sukumar Ghorai, build bot (Jenkins), sridhar siricilla,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/77615?usp=email

to look at the new patch set (#5).

Change subject: soc/intel/common: Fix invalid MADT entries creation
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soc/intel/common: Fix invalid MADT entries creation

commit b793aa3bca5a3f8a6c4ef5a28925a1aeebf426c8 ("soc/intel/common:
Order the CPUs based on their APIC IDs") sort algorithnm walks all the
`cpu_info' entries without discarding empty ones.  Since `cpu_info' is
not initialized, the data that is used is undefined and it generally
results in the creation of invalid `Local x2APIC' entries in the
MADT ("APIC") ACPI table.

Depending on the X2APIC ID value the Linux kernel behavior
changes (cf. arch/x86/kernel/acpi/boot.c::acpi_register_lapic()):
1. If (int)ID >= MAX_LOCAL_APIC (32768), the Linux kernel discards the
   entry with the "skipped apicid that is too big" INFO level
   message.
2. If (int)ID < MAX_LOCAL_APIC (32768) (including negative) this data
   is taken into account and it can lead to undesirable behavior such
   as core being disabled as (cf. "native_cpu_up: bad cpu" ERROR
   kernel message).

TEST=Verified the MADT does not contain any invalid entry on rex.

Change-Id: I19c7aa51f232bf48201bd6d28f108e9120a21f7e
Signed-off-by: Jeremy Compostella 
---
M src/arch/x86/cpu.c
M src/soc/intel/common/block/acpi/cpu_hybrid.c
2 files changed, 3 insertions(+), 1 deletion(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/15/77615/5