The early initcall to initialize the primary thread mask is not longer
required because topology_init_possible_cpus() can mark primary threads
correctly when initializing the possible and present map as the number of
SMT threads is already determined correctly.
The XENPV workaround is not longer required because XENPV now registers
fake APIC IDs which will just work like any other enumeration.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.736104257@linutronix.de
Now that all possible APIC IDs are tracked in the topology bitmaps, its
trivial to retrieve the real information from there.
This gets rid of the guesstimates for the maximal packages and dies per
package as the actual numbers can be determined before a single AP has been
brought up.
The number of SMT threads can now be determined correctly from the bitmaps
in all situations. Up to now a system which has SMT disabled in the BIOS
will still claim that it is SMT capable, because the lowest APIC ID bit is
reserved for that and CPUID leaf 0xb/0x1f still enumerates the SMT domain
accordingly. By calculating the bitmap weights of the SMT and the CORE
domain and setting them into relation the SMT disabled in BIOS situation
reports correctly that the system is not SMT capable.
It also handles the situation correctly when a hybrid systems boot CPU does
not have SMT as it takes the SMT capability of the APs fully into account.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.681709880@linutronix.de
It turns out that XEN/PV Dom0 has halfways usable CPUID/MADT enumeration
except that it cannot deal with CPUs which are enumerated as disabled in
MADT.
DomU has no MADT and provides at least rudimentary topology information in
CPUID leaves 1 and 4.
For both it's important that there are not more possible Linux CPUs than
vCPUs provided by the hypervisor.
As this is ensured by counting the vCPUs before enumeration happens:
- lift the restrictions in the CPUID evaluation and the MADT parser
- Utilize MADT registration for Dom0
- Keep the fake APIC ID registration for DomU
- Fix the XEN APIC fake so the readout of the local APIC ID works for
Dom0 via the hypercall and for DomU by returning the registered
fake APIC IDs.
With that the XEN/PV fake approximates usefulness.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.626195405@linutronix.de
XEN/PV has a completely broken vCPU enumeration scheme, which just works by
chance and provides zero topology information. Each vCPU ends up being a
single core package.
Dom0 provides MADT which can be used for topology information, but that
table is the unmodified host table, which means that there can be more CPUs
registered than the number of vCPUs XEN provides for the dom0 guest.
DomU does not have ACPI and both rely on counting the possible vCPUs via an
hypercall.
To prepare for using CPUID topology information either via MADT or via fake
APIC IDs count the number of possible CPUs during early boot and adjust
nr_cpu_ids() accordingly.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.571795063@linutronix.de
There is no point in assigning the CPU numbers during ACPI physical
hotplug. The number of possible hotplug CPUs is known when the possible map
is initialized, so the CPU numbers can be associated to the registered
non-present APIC IDs right there.
This allows to put more code into the __init section and makes the related
data __ro_after_init.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.517339971@linutronix.de
Topology on X86 is determined by the registered APIC IDs and the
segmentation information retrieved from CPUID. Depending on the granularity
of the provided CPUID information the most fine grained scheme looks like
this according to Intel terminology:
[PKG][DIEGRP][DIE][TILE][MODULE][CORE][THREAD]
Not enumerated domain levels consume 0 bits in the APIC ID. This allows to
provide a consistent view at the topology and determine other information
precisely like the number of cores in a package on hybrid systems, where
the existing assumption that number or cores == number of threads / threads
per core does not hold.
Provide per domain level bitmaps which record the APIC ID split into the
domain levels to make later evaluation of domain level specific information
simple. This allows to calculate e.g. the logical IDs without any further
extra logic.
Contrary to the existing registration mechanism this records disabled CPUs,
which are subject to later hotplug as well. That's useful for boot time
sizing of package or die dependent allocations without using heuristics.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.406985021@linutronix.de
When a kdump kernel is started from a crashing CPU then there is no
guarantee that this CPU is the real boot CPU (BSP). If the kdump kernel
tries to online the BSP then the INIT sequence will reset the machine.
There is a command line option to prevent this, but in case of nested kdump
kernels this is wrong.
But that command line option is not required at all because the real
BSP is enumerated as the first CPU by firmware. Support for the only
known system which was different (Voyager) got removed long ago.
Detect whether the boot CPU APIC ID is the first APIC ID enumerated by
the firmware. If the first APIC ID enumerated is not matching the boot
CPU APIC ID then skip registering it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.348542071@linutronix.de
Managing possible CPUs is an unreadable and uncomprehensible maze. Aside of
that it's backwards because it applies command line limits after
registering all APICs.
Rewrite it so that it:
- Applies the command line limits upfront so that only the allowed amount
of APIC IDs can be registered.
- Applies eventual late restrictions in an understandable way
- Uses simple min_t() calculations which are trivial to follow.
- Provides a separate function for resetting to UP mode late in the
bringup process.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.290098853@linutronix.de
Having the same check whether the number of assigned CPUs has reached the
nr_cpu_ids limit twice in the same code path is pointless. Repeating the
information that CPUs are ignored over and over is also pointless noise.
Remove the redundant check and reduce the noise by using a pr_warn_once().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210252.050264369@linutronix.de
XENPV does not use the APIC. It's just piggy packing on the infrastructure
and fiddles with global variables as it sees fit.
These global variables are going away, so let XENPV register pseudo APIC
IDs to keep the accounting correct and keep up the illusion that XEN/PV is
something sane.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210251.940043512@linutronix.de
The MADT table for XEN/PV dom0 is not really useful and registering the
APICs is momentarily a pointless exercise because XENPV does not use an
APIC at all.
It overrides the x86_init.mpparse.parse_smp_config() callback, resets
num_processors and counts how many of them are provided by the hypervisor.
This is in the way of cleaning up the APIC registration. Prevent MADT
registration for XEN/PV temporarily until the rework is completed and
XEN/PV can use the MADT again.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210251.885489468@linutronix.de
generic_processor_info() aside of being a complete misnomer is used for
both early boot registration and ACPI CPU hotplug.
While it's arguable that this can share some code, it results in code which
is hard to understand and kept around post init for no real reason.
Also the call sites do lots of manual fiddling in topology related
variables instead of having proper interfaces for the purpose which handle
the topology internals correctly.
Provide topology_register_apic(), topology_hotplug_apic() and
topology_hotunplug_apic() which have the extra magic of the call sites
incorporated and for now are wrappers around generic_processor_info().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240213210251.605007456@linutronix.de
Paranoia is not wrong, but having an APIC callback which is in most
implementations a complete NOOP and in one actually looking whether the
APICID of an upcoming CPU has been registered. The same APICID which was
used to bring the CPU out of wait for startup.
That's paranoia for the paranoia sake. Remove the voodoo.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240212154640.116510935@linutronix.de
There is no reason to have the early mptable evaluation conditionally
invoked only from the AMD numa topology code.
Make it explicit and invoke it from setup_arch() right after the
corresponding ACPI init call. Remove the pointless wrapper and invoke
x86_init::mpparse::early_parse_smp_config() directly.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240212154639.931761608@linutronix.de
