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linux/arch/x86/kernel
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Waiman Long 2743fe89d4 x86/idle: Disable IBRS when CPU is offline to improve single-threaded performance 
Commit bf5835bcdb ("intel_idle: Disable IBRS during long idle")
disables IBRS when the CPU enters long idle. However, when a CPU
becomes offline, the IBRS bit is still set when X86_FEATURE_KERNEL_IBRS
is enabled. That will impact the performance of a sibling CPU. Mitigate
this performance impact by clearing all the mitigation bits in SPEC_CTRL
MSR when offline. When the CPU is online again, it will be re-initialized
and so restoring the SPEC_CTRL value isn't needed.

Add a comment to say that native_play_dead() is a __noreturn function,
but it can't be marked as such to avoid confusion about the missing
MSR restoration code.

When DPDK is running on an isolated CPU thread processing network packets
in user space while its sibling thread is idle. The performance of the
busy DPDK thread with IBRS on and off in the sibling idle thread are:

                                IBRS on         IBRS off
                                -------         --------
  packets/second:                  7.8M           10.4M
  avg tsc cycles/packet:         282.26          209.86

This is a 25% performance degradation. The test system is a Intel Xeon
4114 CPU @ 2.20GHz.

[ mingo: Extended the changelog with performance data from the 0/4 mail. ]

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20230727184600.26768-3-longman@redhat.com
2023-10-07 11:33:28 +02:00
..
acpi * Rework apic callbacks, getting rid of unnecessary ones and 2023-08-30 10:44:46 -07:00
apic x86/platform/uv: Use alternate source for socket to node data 2023-09-11 10:06:22 -07:00
cpu x86/sgx: Resolves SECS reclaim vs. page fault for EAUG race 2023-09-28 16:16:40 -07:00
fpu * Mark all Skylake CPUs as vulnerable to GDS 2023-09-01 16:40:19 -07:00
kprobes X86 core updates: 2023-08-30 10:10:31 -07:00
.gitignore
alternative.c x86,static_call: Fix static-call vs return-thunk 2023-09-22 18:58:24 +02:00
amd_gart_64.c x86/mm: Remove P*D_PAGE_MASK and P*D_PAGE_SIZE macros 2022-12-15 10:37:27 -08:00
amd_nb.c x86/amd_nb: Add PCI IDs for AMD Family 1Ah-based models 2023-08-10 14:12:48 +02:00
aperture_64.c x86: Fix various duplicate-word comment typos 2022-08-15 19:17:52 +02:00
apm_32.c x86/APM: drop the duplicate APM_MINOR_DEV macro 2023-07-30 14:00:32 +02:00
asm-offsets.c x86/smpboot: Remove initial_stack on 64-bit 2023-03-21 13:35:53 +01:00
asm-offsets_32.c x86/stackprotector/32: Make the canary into a regular percpu variable 2021-03-08 13:19:05 +01:00
asm-offsets_64.c x86: Fixup asm-offsets duplicate 2022-10-17 16:41:06 +02:00
audit_64.c x86/audit: Fix -Wmissing-variable-declarations warning for ia32_xyz_class 2023-08-30 10:11:16 +02:00
bootflag.c
callthunks.c x86,static_call: Fix static-call vs return-thunk 2023-09-22 18:58:24 +02:00
cet.c x86/ibt: Convert IBT selftest to asm 2023-08-17 17:07:09 +02:00
cfi.c x86: Add support for CONFIG_CFI_CLANG 2022-09-26 10:13:16 -07:00
check.c
cpuid.c x86/cpuid: make cpuid_class a static const structure 2023-08-05 08:31:41 +02:00
crash.c ARM: 2023-09-07 13:52:20 -07:00
crash_core_32.c
crash_core_64.c
crash_dump_32.c vmcore: convert copy_oldmem_page() to take an iov_iter 2022-04-29 14:37:59 -07:00
crash_dump_64.c use less confusing names for iov_iter direction initializers 2022-11-25 13:01:55 -05:00
devicetree.c x86/apic: Make some APIC init functions bool 2023-08-09 11:58:20 -07:00
doublefault_32.c x86: Avoid missing-prototype warnings for doublefault code 2023-05-18 11:56:18 -07:00
dumpstack.c x86/show_trace_log_lvl: Ensure stack pointer is aligned, again 2023-05-16 06:31:04 -07:00
dumpstack_32.c x86/percpu: Move irq_stack variables next to current_task 2022-10-17 16:41:05 +02:00
dumpstack_64.c x86/percpu: Move irq_stack variables next to current_task 2022-10-17 16:41:05 +02:00
e820.c x86/setup: Move duplicate boot_cpu_data definition out of the ifdeffery 2023-01-11 12:45:16 +01:00
early-quirks.c drm/i915/rpl-p: Add PCI IDs 2022-04-19 17:14:09 -07:00
early_printk.c x86/earlyprintk: Clean up pciserial 2022-08-29 12:19:25 +02:00
ebda.c
eisa.c
espfix_64.c x86/espfix: Use get_random_long() rather than archrandom 2022-10-31 20:12:50 +01:00
ftrace.c x86/ftrace: Remove unsued extern declaration ftrace_regs_caller_ret() 2023-07-10 21:38:13 -04:00
ftrace_32.S x86/ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL 2023-06-20 18:38:38 -04:00
ftrace_64.S x86/ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL 2023-06-20 18:38:38 -04:00
head32.c x86: Add dummy prototype for mk_early_pgtbl_32() 2023-05-18 11:56:16 -07:00
head64.c x86/head: Mark *_start_kernel() __noreturn 2023-04-14 17:31:24 +02:00
head_32.S x86/smpboot: Restrict soft_restart_cpu() to SEV 2023-05-15 13:44:50 +02:00
head_64.S x86/head_64: Store boot_params pointer in callee save register 2023-08-07 19:20:32 +02:00
hpet.c x86/hpet: Refactor code using deprecated strncpy() interface to use strscpy() 2023-08-24 21:22:40 +02:00
hw_breakpoint.c x86/amd: Cache debug register values in percpu variables 2023-01-31 20:09:26 +01:00
i8237.c
i8253.c
i8259.c x86/irq/i8259: Fix kernel-doc annotation warning 2023-08-31 20:43:30 +02:00
ibt_selftest.S x86/ibt: Convert IBT selftest to asm 2023-08-17 17:07:09 +02:00
idt.c Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
io_delay.c
ioport.c
irq.c x86/apic: Nuke ack_APIC_irq() 2023-08-09 11:58:34 -07:00
irq_32.c x86/percpu: Move irq_stack variables next to current_task 2022-10-17 16:41:05 +02:00
irq_64.c x86/percpu: Move irq_stack variables next to current_task 2022-10-17 16:41:05 +02:00
irq_work.c x86/apic: Wrap IPI calls into helper functions 2023-08-09 12:00:55 -07:00
irqflags.S x86: Prepare asm files for straight-line-speculation 2021-12-08 12:25:37 +01:00
irqinit.c x86/i8259: Mark legacy PIC interrupts with IRQ_LEVEL 2023-01-16 17:24:56 +01:00
itmt.c x86/sched/itmt: Give all SMT siblings of a core the same priority 2023-05-08 10:58:38 +02:00
jailhouse.c x86/apic: Remove the pointless APIC version check 2023-08-09 11:58:19 -07:00
jump_label.c jump_label: make initial NOP patching the special case 2022-06-24 09:48:55 +02:00
kdebugfs.c x86/boot: Fix memremap of setup_indirect structures 2022-03-09 12:49:44 +01:00
kexec-bzimage64.c docs: move x86 documentation into Documentation/arch/ 2023-03-30 12:58:51 -06:00
kgdb.c x86/kgdb: Fix a kerneldoc warning when build with W=1 2023-09-24 11:00:13 +02:00
ksysfs.c x86/boot: Fix memremap of setup_indirect structures 2022-03-09 12:49:44 +01:00
kvm.c * Rework apic callbacks, getting rid of unnecessary ones and 2023-08-30 10:44:46 -07:00
kvmclock.c x86/tsc: Provide sched_clock_noinstr() 2023-06-05 21:11:08 +02:00
ldt.c x86: allow get_locked_pte() to fail 2023-06-19 16:19:10 -07:00
machine_kexec_32.c x86/kexec: Set_[gi]dt() -> native_[gi]dt_invalidate() in machine_kexec_*.c 2021-05-21 12:36:45 +02:00
machine_kexec_64.c x86/kexec: remove unnecessary arch_kexec_kernel_image_load() 2023-04-08 13:45:38 -07:00
Makefile Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
mmconf-fam10h_64.c x86/msr: Rename MSR_K8_SYSCFG to MSR_AMD64_SYSCFG 2021-05-10 07:51:38 +02:00
module.c x86/alternative: Rename apply_ibt_endbr() 2023-07-10 09:52:23 +02:00
mpparse.c x86/apic: Sanitize APIC address setup 2023-08-09 11:58:20 -07:00
msr.c x86/MSR: make msr_class a static const structure 2023-08-05 08:31:42 +02:00
nmi.c locking/atomic: treewide: use raw_atomic*_<op>() 2023-06-05 09:57:20 +02:00
nmi_selftest.c x86/apic: Wrap IPI calls into helper functions 2023-08-09 12:00:55 -07:00
paravirt-spinlocks.c x86/paravirt: Add new features for paravirt patching 2021-03-11 19:51:49 +01:00
paravirt.c x86/xen: move paravirt lazy code 2023-09-19 07:04:49 +02:00
pci-dma.c x86: always initialize xen-swiotlb when xen-pcifront is enabling 2023-07-31 17:54:27 +02:00
pcspeaker.c
perf_regs.c - Remove all uses of TIF_IA32 and TIF_X32 and reclaim the two bits in the end 2020-12-14 13:45:26 -08:00
platform-quirks.c x86/quirks: Include linux/pnp.h for arch_pnpbios_disabled() 2023-05-18 11:56:18 -07:00
pmem.c x86/pmem: Fix platform-device leak in error path 2022-06-20 18:01:16 +02:00
probe_roms.c x86/kernel: Validate ROM memory before accessing when SEV-SNP is active 2022-04-06 13:23:09 +02:00
process.c x86/shstk: Remove useless clone error handling 2023-09-19 09:18:34 -07:00
process.h x86: Snapshot thread flags 2021-12-01 00:06:43 +01:00
process_32.c x86/resctl: fix scheduler confusion with 'current' 2023-03-08 11:48:11 -08:00
process_64.c x86/shstk: Add ARCH_SHSTK_STATUS 2023-08-02 15:01:51 -07:00
ptrace.c x86: Add PTRACE interface for shadow stack 2023-08-02 15:01:51 -07:00
pvclock.c locking/atomic: treewide: use raw_atomic*_<op>() 2023-06-05 09:57:20 +02:00
quirks.c x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user, kernel}() 2020-10-06 11:18:04 +02:00
reboot.c x86/reboot: Expose VMCS crash hooks if and only if KVM_{INTEL,AMD} is enabled 2023-08-03 15:37:14 -07:00
reboot_fixups_32.c
relocate_kernel_32.S x86/kexec: Disable RET on kexec 2022-07-09 13:12:32 +02:00
relocate_kernel_64.S x86,objtool: Split UNWIND_HINT_EMPTY in two 2023-03-23 23:18:58 +01:00
resource.c x86/PCI: Tidy E820 removal messages 2022-12-10 10:33:11 -06:00
rethook.c x86,rethook: Fix arch_rethook_trampoline() to generate a complete pt_regs 2022-03-28 19:38:51 -07:00
rtc.c x86/rtc: Simplify PNP ids check 2023-01-06 04:22:34 +01:00
setup.c x86/mm, kexec, ima: Use memblock_free_late() from ima_free_kexec_buffer() 2023-09-18 09:24:15 +02:00
setup_percpu.c x86/apic/32: Remove x86_cpu_to_logical_apicid 2023-08-09 11:58:23 -07:00
sev-shared.c x86/sev: Add SNP-specific unaccepted memory support 2023-06-06 18:31:37 +02:00
sev.c * Rework apic callbacks, getting rid of unnecessary ones and 2023-08-30 10:44:46 -07:00
sev_verify_cbit.S x86: Prepare asm files for straight-line-speculation 2021-12-08 12:25:37 +01:00
shstk.c x86/shstk: Add warning for shadow stack double unmap 2023-09-19 09:18:34 -07:00
signal.c x86/shstk: Handle signals for shadow stack 2023-08-02 15:01:50 -07:00
signal_32.c x86/shstk: Add user control-protection fault handler 2023-08-02 15:01:50 -07:00
signal_64.c x86/shstk: Handle signals for shadow stack 2023-08-02 15:01:50 -07:00
smp.c x86/apic: Wrap IPI calls into helper functions 2023-08-09 12:00:55 -07:00
smpboot.c x86/idle: Disable IBRS when CPU is offline to improve single-threaded performance 2023-10-07 11:33:28 +02:00
stacktrace.c x86: remove __range_not_ok() 2022-02-25 09:36:05 +01:00
static_call.c x86/static_call: Fix __static_call_fixup() 2023-08-17 13:24:09 +02:00
step.c ptrace: Reimplement PTRACE_KILL by always sending SIGKILL 2022-05-11 14:34:28 -05:00
sys_ia32.c x86: switch to kernel_clone() 2020-08-20 13:12:58 +02:00
sys_x86_64.c x86/mm: Introduce MAP_ABOVE4G 2023-07-11 14:12:19 -07:00
tboot.c mm: remove rb tree. 2022-09-26 19:46:16 -07:00
time.c
tls.c x86/gsseg: Move load_gs_index() to its own new header file 2023-01-12 13:06:36 +01:00
tls.h x86: switch to ->regset_get() 2020-07-27 14:31:07 -04:00
topology.c x86/topology: Remove CPU0 hotplug option 2023-05-15 13:44:49 +02:00
trace.c trace/osnoise: Fix an ifdef comment 2021-10-25 23:02:36 -04:00
trace_clock.c
tracepoint.c x86/traceponit: Fix comment about irq vector tracepoints 2022-05-26 22:03:52 -04:00
traps.c Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
tsc.c x86/tsc: Extend watchdog check exemption to 4-Sockets platform 2023-07-14 15:17:09 -07:00
tsc_msr.c Misc fixes and small updates all around the place: 2020-08-15 10:38:03 -07:00
tsc_sync.c x86/smpboot: Make TSC synchronization function call based 2023-05-15 13:44:53 +02:00
umip.c x86/umip: Downgrade warning messages to debug loglevel 2021-09-25 13:23:28 +02:00
unwind_frame.c x86: kmsan: don't instrument stack walking functions 2022-10-03 14:03:25 -07:00
unwind_guess.c x86/unwind: Recover kretprobe trampoline entry 2021-09-30 21:24:07 -04:00
unwind_orc.c objtool changes for v6.5: 2023-06-27 15:05:41 -07:00
uprobes.c uprobes/x86: Allow to probe a NOP instruction with 0x66 prefix 2022-12-05 11:55:18 +01:00
verify_cpu.S x86: Prepare asm files for straight-line-speculation 2021-12-08 12:25:37 +01:00
vm86_32.c x86/32: Remove lazy GS macros 2022-04-14 14:09:43 +02:00
vmlinux.lds.S x86/build: Fix linker fill bytes quirk/incompatibility for ld.lld 2023-09-06 23:49:12 +02:00
vsmp_64.c x86/apic: Get rid of hard_smp_processor_id() 2023-08-09 11:58:17 -07:00
x86_init.c - Fix a race window where load_unaligned_zeropad() could cause 2023-06-26 16:32:47 -07:00