- Fix the incorrect handling of atomic offset updates in
reserve_eilvt_offset()
The check for the return value of atomic_cmpxchg() is not compared
against the old value, it is compared against the new value, which
makes it two round on success.
Convert it to atomic_try_cmpxchg() which does the right thing.
- Handle IO/APIC less systems correctly
When IO/APIC is not advertised by ACPI then the computation of the lower
bound for dynamically allocated interrupts like MSI goes wrong.
This lower bound is used to exclude the IO/APIC legacy GSI space as that
must stay reserved for the legacy interrupts.
In case that the system, e.g. VM, does not advertise an IO/APIC the
lower bound stays at 0.
0 is an invalid interrupt number except for the legacy timer interrupt
on x86. The return value is unchecked in the core code, so it ends up
to allocate interrupt number 0 which is subsequently considered to be
invalid by the caller, e.g. the MSI allocation code.
A similar problem was already cured for device tree based systems years
ago, but that missed - or did not envision - the zero IO/APIC case.
Consolidate the zero check and return the provided "from" argument to the
core code call site, which is guaranteed to be greater than 0.
- Simplify the X2APIC cluster CPU mask logic for CPU hotplug
Per cluster CPU masks are required for X2APIC in cluster mode to
determine the correct cluster for a target CPU when calculating the
destination for IPIs
These masks are established when CPUs are borught up. The first CPU in a
cluster must allocate a new cluster CPU mask. As this happens during the
early startup of a CPU, where memory allocations cannot be done, the
mask has to be allocated by the control CPU.
The current implementation allocates a clustermask just in case and if
the to be brought up CPU is the first in a cluster the CPU takes over
this allocation from a global pointer.
This works nicely in the fully serialized CPU bringup scenario which is
used today, but would fail completely for parallel bringup of CPUs.
The cluster association of a CPU can be computed from the APIC ID which
is enumerated by ACPI/MADT.
So the cluster CPU masks can be preallocated and associated upfront and
the upcoming CPUs just need to set their corresponding bit.
Aside of preparing for parallel bringup this is a valuable
simplification on its own.
- Remove global variables which control the early startup of secondary
CPUs on 64-bit
The only information which is needed by a starting CPU is the Linux CPU
number. The CPU number allows it to retrieve the rest of the required
data from already existing per CPU storage.
So instead of initial_stack, early_gdt_desciptor and initial_gs provide
a new variable smpboot_control which contains the Linux CPU number for
now. The starting CPU can retrieve and compute all required information
for startup from there.
Aside of being a cleanup, this is also preparing for parallel CPU
bringup, where starting CPUs will look up their Linux CPU number via the
APIC ID, when smpboot_control has the corresponding control bit set.
- Make cc_vendor globally accesible
Subsequent parallel bringup changes require access to cc_vendor because
confidental computing platforms need special treatment in the early
startup phase vs. CPUID and APCI ID readouts.
The change makes cc_vendor global and provides stub accessors in case
that CONFIG_ARCH_HAS_CC_PLATFORM is not set.
This was merged from the x86/cc branch in anticipation of further
parallel bringup commits which require access to cc_vendor. Due to late
discoveries of fundamental issue with those patches these commits never
happened.
The merge commit is unfortunately in the middle of the APIC commits so
unraveling it would have required a rebase or revert. As the parallel
bringup seems to be well on its way for 6.5 this would be just pointless
churn. As the commit does not contain any functional change it's not a
risk to keep it.