summaryrefslogtreecommitdiff
path: root/Documentation
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2024-03-12 01:45:55 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2024-03-12 01:45:55 +0300
commitca7e917769121195bae45d4886f6e24efd6f99ae (patch)
tree9f5b2f75f27697f83b0e214889327221bd503a6a /Documentation
parentd08c407f715f651e7ea40b3a037be46dd2b11e4c (diff)
parentf0551af021308a2a1163dc63d1f1bba3594208bd (diff)
downloadlinux-ca7e917769121195bae45d4886f6e24efd6f99ae.tar.xz
Merge tag 'x86-apic-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 APIC updates from Thomas Gleixner: "Rework of APIC enumeration and topology evaluation. The current implementation has a couple of shortcomings: - It fails to handle hybrid systems correctly. - The APIC registration code which handles CPU number assignents is in the middle of the APIC code and detached from the topology evaluation. - The various mechanisms which enumerate APICs, ACPI, MPPARSE and guest specific ones, tweak global variables as they see fit or in case of XENPV just hack around the generic mechanisms completely. - The CPUID topology evaluation code is sprinkled all over the vendor code and reevaluates global variables on every hotplug operation. - There is no way to analyze topology on the boot CPU before bringing up the APs. This causes problems for infrastructure like PERF which needs to size certain aspects upfront or could be simplified if that would be possible. - The APIC admission and CPU number association logic is incomprehensible and overly complex and needs to be kept around after boot instead of completing this right after the APIC enumeration. This update addresses these shortcomings with the following changes: - Rework the CPUID evaluation code so it is common for all vendors and provides information about the APIC ID segments in a uniform way independent of the number of segments (Thread, Core, Module, ..., Die, Package) so that this information can be computed instead of rewriting global variables of dubious value over and over. - A few cleanups and simplifcations of the APIC, IO/APIC and related interfaces to prepare for the topology evaluation changes. - Seperation of the parser stages so the early evaluation which tries to find the APIC address can be seperately overridden from the late evaluation which enumerates and registers the local APIC as further preparation for sanitizing the topology evaluation. - A new registration and admission logic which - encapsulates the inner workings so that parsers and guest logic cannot longer fiddle in it - uses the APIC ID segments to build topology bitmaps at registration time - provides a sane admission logic - allows to detect the crash kernel case, where CPU0 does not run on the real BSP, automatically. This is required to prevent sending INIT/SIPI sequences to the real BSP which would reset the whole machine. This was so far handled by a tedious command line parameter, which does not even work in nested crash scenarios. - Associates CPU number after the enumeration completed and prevents the late registration of APICs, which was somehow tolerated before. - Converting all parsers and guest enumeration mechanisms over to the new interfaces. This allows to get rid of all global variable tweaking from the parsers and enumeration mechanisms and sanitizes the XEN[PV] handling so it can use CPUID evaluation for the first time. - Mopping up existing sins by taking the information from the APIC ID segment bitmaps. This evaluates hybrid systems correctly on the boot CPU and allows for cleanups and fixes in the related drivers, e.g. PERF. The series has been extensively tested and the minimal late fallout due to a broken ACPI/MADT table has been addressed by tightening the admission logic further" * tag 'x86-apic-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (76 commits) x86/topology: Ignore non-present APIC IDs in a present package x86/apic: Build the x86 topology enumeration functions on UP APIC builds too smp: Provide 'setup_max_cpus' definition on UP too smp: Avoid 'setup_max_cpus' namespace collision/shadowing x86/bugs: Use fixed addressing for VERW operand x86/cpu/topology: Get rid of cpuinfo::x86_max_cores x86/cpu/topology: Provide __num_[cores|threads]_per_package x86/cpu/topology: Rename topology_max_die_per_package() x86/cpu/topology: Rename smp_num_siblings x86/cpu/topology: Retrieve cores per package from topology bitmaps x86/cpu/topology: Use topology logical mapping mechanism x86/cpu/topology: Provide logical pkg/die mapping x86/cpu/topology: Simplify cpu_mark_primary_thread() x86/cpu/topology: Mop up primary thread mask handling x86/cpu/topology: Use topology bitmaps for sizing x86/cpu/topology: Let XEN/PV use topology from CPUID/MADT x86/xen/smp_pv: Count number of vCPUs early x86/cpu/topology: Assign hotpluggable CPUIDs during init x86/cpu/topology: Reject unknown APIC IDs on ACPI hotplug x86/topology: Add a mechanism to track topology via APIC IDs ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/kdump/kdump.rst7
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt9
-rw-r--r--Documentation/arch/x86/topology.rst24
3 files changed, 11 insertions, 29 deletions
diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
index 5762e7477a0c..0302a93b1d40 100644
--- a/Documentation/admin-guide/kdump/kdump.rst
+++ b/Documentation/admin-guide/kdump/kdump.rst
@@ -191,9 +191,7 @@ Dump-capture kernel config options (Arch Dependent, i386 and x86_64)
CPU is enough for kdump kernel to dump vmcore on most of systems.
However, you can also specify nr_cpus=X to enable multiple processors
- in kdump kernel. In this case, "disable_cpu_apicid=" is needed to
- tell kdump kernel which cpu is 1st kernel's BSP. Please refer to
- admin-guide/kernel-parameters.txt for more details.
+ in kdump kernel.
With CONFIG_SMP=n, the above things are not related.
@@ -454,8 +452,7 @@ Notes on loading the dump-capture kernel:
to use multi-thread programs with it, such as parallel dump feature of
makedumpfile. Otherwise, the multi-thread program may have a great
performance degradation. To enable multi-cpu support, you should bring up an
- SMP dump-capture kernel and specify maxcpus/nr_cpus, disable_cpu_apicid=[X]
- options while loading it.
+ SMP dump-capture kernel and specify maxcpus/nr_cpus options while loading it.
* For s390x there are two kdump modes: If a ELF header is specified with
the elfcorehdr= kernel parameter, it is used by the kdump kernel as it
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 06de88a27900..8a081ac79808 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1095,15 +1095,6 @@
Disable TLBIE instruction. Currently does not work
with KVM, with HASH MMU, or with coherent accelerators.
- disable_cpu_apicid= [X86,APIC,SMP]
- Format: <int>
- The number of initial APIC ID for the
- corresponding CPU to be disabled at boot,
- mostly used for the kdump 2nd kernel to
- disable BSP to wake up multiple CPUs without
- causing system reset or hang due to sending
- INIT from AP to BSP.
-
disable_ddw [PPC/PSERIES,EARLY]
Disable Dynamic DMA Window support. Use this
to workaround buggy firmware.
diff --git a/Documentation/arch/x86/topology.rst b/Documentation/arch/x86/topology.rst
index 08ebf9edbfc1..7352ab89a55a 100644
--- a/Documentation/arch/x86/topology.rst
+++ b/Documentation/arch/x86/topology.rst
@@ -47,17 +47,21 @@ AMD nomenclature for package is 'Node'.
Package-related topology information in the kernel:
- - cpuinfo_x86.x86_max_cores:
+ - topology_num_threads_per_package()
- The number of cores in a package. This information is retrieved via CPUID.
+ The number of threads in a package.
- - cpuinfo_x86.x86_max_dies:
+ - topology_num_cores_per_package()
- The number of dies in a package. This information is retrieved via CPUID.
+ The number of cores in a package.
+
+ - topology_max_dies_per_package()
+
+ The maximum number of dies in a package.
- cpuinfo_x86.topo.die_id:
- The physical ID of the die. This information is retrieved via CPUID.
+ The physical ID of the die.
- cpuinfo_x86.topo.pkg_id:
@@ -96,16 +100,6 @@ are SMT- or CMT-type threads.
AMDs nomenclature for a CMT core is "Compute Unit". The kernel always uses
"core".
-Core-related topology information in the kernel:
-
- - smp_num_siblings:
-
- The number of threads in a core. The number of threads in a package can be
- calculated by::
-
- threads_per_package = cpuinfo_x86.x86_max_cores * smp_num_siblings
-
-
Threads
=======
A thread is a single scheduling unit. It's the equivalent to a logical Linux