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Paul Mackerras 7672691a08 powerpc/powernv: Provide a way to force a core into SMT4 mode 
POWER9 processors up to and including "Nimbus" v2.2 have hardware
bugs relating to transactional memory and thread reconfiguration.
One of these bugs has a workaround which is to get the core into
SMT4 state temporarily.  This workaround is only needed when
running bare-metal.

This patch provides a function which gets the core into SMT4 mode
by preventing threads from going to a stop state, and waking up
those which are already in a stop state.  Once at least 3 threads
are not in a stop state, the core will be in SMT4 and we can
continue.

To do this, we add a "dont_stop" flag to the paca to tell the
thread not to go into a stop state.  If this flag is set,
power9_idle_stop() just returns immediately with a return value
of 0.  The pnv_power9_force_smt4_catch() function does the following:

1. Set the dont_stop flag for each thread in the core, except
   ourselves (in fact we use an atomic_inc() in case more than
   one thread is calling this function concurrently).
2. See how many threads are awake, indicated by their
   requested_psscr field in the paca being 0.  If this is at
   least 3, skip to step 5.
3. Send a doorbell interrupt to each thread that was seen as
   being in a stop state in step 2.
4. Until at least 3 threads are awake, scan the threads to which
   we sent a doorbell interrupt and check if they are awake now.

This relies on the following properties:

- Once dont_stop is non-zero, requested_psccr can't go from zero to
  non-zero, except transiently (and without the thread doing stop).
- requested_psscr being zero guarantees that the thread isn't in
  a state-losing stop state where thread reconfiguration could occur.
- Doing stop with a PSSCR value of 0 won't be a state-losing stop
  and thus won't allow thread reconfiguration.
- Once threads_per_core/2 + 1 (i.e. 3) threads are awake, the core
  must be in SMT4 mode, since SMT modes are powers of 2.

This does add a sync to power9_idle_stop(), which is necessary to
provide the correct ordering between setting requested_psscr and
checking dont_stop.  The overhead of the sync should be unnoticeable
compared to the latency of going into and out of a stop state.

Because some objected to incurring this extra latency on systems where
the XER[SO] bug is not relevant, I have put the test in
power9_idle_stop inside a feature section.  This means that
pnv_power9_force_smt4_catch() WILL NOT WORK correctly on systems
without the CPU_FTR_P9_TM_XER_SO_BUG feature bit set, and will
probably hang the system.

In order to cater for uses where the caller has an operation that
has to be done while the core is in SMT4, the core continues to be
kept in SMT4 after pnv_power9_force_smt4_catch() function returns,
until the pnv_power9_force_smt4_release() function is called.
It undoes the effect of step 1 above and allows the other threads
to go into a stop state.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2018-03-24 00:39:11 +11:00
..
trace powerpc updates for 4.15 2017-11-16 12:47:46 -08:00
vdso32 License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
vdso64 powerpc/vdso64: Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE 2017-12-04 15:01:09 +11:00
.gitignore
align.c powerpc: Fix check for copy/paste instructions in alignment handler 2017-10-25 12:42:35 +02:00
asm-offsets.c powerpc/powernv: Provide a way to force a core into SMT4 mode 2018-03-24 00:39:11 +11:00
audit.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
btext.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cacheinfo.c powerpc: Convert to using %pOF instead of full_name 2017-08-23 22:27:04 +10:00
cacheinfo.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
compat_audit.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cpu_setup_6xx.S powerpc: Free up CPU feature bits on 64-bit machines 2018-03-24 00:38:51 +11:00
cpu_setup_44x.S
cpu_setup_fsl_booke.S powerpc: Free up CPU feature bits on 64-bit machines 2018-03-24 00:38:51 +11:00
cpu_setup_pa6t.S
cpu_setup_power.S Merge branch 'fixes' into next 2018-01-21 23:21:14 +11:00
cpu_setup_ppc970.S
cputable.c powerpc: Add CPU feature bits for TM bug workarounds on POWER9 v2.2 2018-03-24 00:39:09 +11:00
crash_dump.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
crash.c powernv/kdump: Fix cases where the kdump kernel can get HMI's 2018-01-16 23:47:11 +11:00
dbell.c powerpc: Introduce msgsnd/doorbell barrier primitives 2017-04-13 23:34:33 +10:00
dma-iommu.c powerpc: rename dma_direct_ to dma_nommu_ 2018-01-10 16:41:14 +01:00
dma-swiotlb.c swiotlb: rename swiotlb_free to swiotlb_exit 2018-01-15 09:35:39 +01:00
dma.c powerpc: rename swiotlb_dma_ops 2018-01-15 09:35:26 +01:00
dt_cpu_ftrs.c powerpc: Add CPU feature bits for TM bug workarounds on POWER9 v2.2 2018-03-24 00:39:09 +11:00
eeh_cache.c powerpc/eeh: Fix pr_debug()s in eeh_cache.c 2016-07-08 22:09:50 +10:00
eeh_dev.c powerpc/eeh: Create PHB PEs after EEH is initialized 2017-09-21 14:56:00 +10:00
eeh_driver.c PCI/AER: Add uevents in AER and EEH error/resume 2018-01-27 20:02:51 +11:00
eeh_event.c powerpc/pci: Always print PHB and PE numbers as hexadecimal 2016-11-22 11:57:07 +11:00
eeh_pe.c powerpc/eeh: Stop using do_gettimeofday() 2017-11-06 17:40:00 +11:00
eeh_sysfs.c powerpc/eeh: Add EEH notify resume sysfs 2018-01-27 20:02:52 +11:00
eeh.c pci-v4.16-changes 2018-02-06 09:59:40 -08:00
entry_32.S powerpc/8xx: Only perform perf counting when perf is in use. 2018-01-16 23:47:12 +11:00
entry_64.S Merge branch 'fixes' into next 2018-01-21 23:21:14 +11:00
epapr_hcalls.S ppc: move exports to definitions 2016-08-07 23:50:09 -04:00
epapr_paravirt.c
exceptions-64e.S powerpc/64: Rename soft_enabled to irq_soft_mask 2018-01-19 22:37:01 +11:00
exceptions-64s.S powerpc/64s: Improve RFI L1-D cache flush fallback 2018-01-23 16:16:33 +11:00
fadump.c Revert "powerpc: Do not call ppc_md.panic in fadump panic notifier" 2017-12-05 23:21:46 +11:00
firmware.c
fpu.S Merge branch 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild 2016-10-14 14:26:58 -07:00
fsl_booke_entry_mapping.S License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
head_8xx.S powerpc/8xx: Use L1 entry APG to handle _PAGE_ACCESSED for CONFIG_SWAP 2018-01-16 23:47:15 +11:00
head_32.S powerpc: Fix DABR match on hash based systems 2017-11-13 22:12:48 +11:00
head_40x.S ppc: move exports to definitions 2016-08-07 23:50:09 -04:00
head_44x.S ppc: move exports to definitions 2016-08-07 23:50:09 -04:00
head_64.S powerpc/64: Rename soft_enabled to irq_soft_mask 2018-01-19 22:37:01 +11:00
head_booke.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
head_fsl_booke.S ppc: move exports to definitions 2016-08-07 23:50:09 -04:00
hw_breakpoint.c Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/scottwood/linux into next 2017-02-18 21:37:14 +11:00
idle_6xx.S
idle_book3e.S powerpc/64: Rename soft_enabled to irq_soft_mask 2018-01-19 22:37:01 +11:00
idle_book3s.S powerpc/powernv: Provide a way to force a core into SMT4 mode 2018-03-24 00:39:11 +11:00
idle_e500.S powerpc/e500mc: Remove dead L2 flushing code in idle_e500.S 2015-06-02 21:37:19 -05:00
idle_power4.S powerpc/64: Rename soft_enabled to irq_soft_mask 2018-01-19 22:37:01 +11:00
idle.c
ima_kexec.c powerpc: ima: send the kexec buffer to the next kernel 2016-12-20 09:48:44 -08:00
io-workarounds.c powerpc: Convert to using %pOF instead of full_name 2017-08-23 22:27:04 +10:00
io.c
iomap.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
iommu.c powerpc/iommu: Use permission-specific DEVICE_ATTR variants 2017-09-01 16:42:54 +10:00
irq.c powerpc: Add new kconfig CONFIG_PPC_IRQ_SOFT_MASK_DEBUG 2018-01-19 22:37:03 +11:00
isa-bridge.c powerpc: Convert to using %pOF instead of full_name 2017-08-23 22:27:04 +10:00
jump_label.c jump_label: Rename JUMP_LABEL_{EN,DIS}ABLE to JUMP_LABEL_{JMP,NOP} 2015-08-03 11:34:12 +02:00
kexec_elf_64.c powerpc: ima: send the kexec buffer to the next kernel 2016-12-20 09:48:44 -08:00
kgdb.c powerpc/8xx: Getting rid of remaining use of CONFIG_8xx 2017-08-10 23:32:12 +10:00
kprobes-ftrace.c powerpc/kprobes: Do not disable interrupts for optprobes and kprobes_on_ftrace 2017-11-12 23:51:41 +11:00
kprobes.c powerpc/kprobes: refactor kprobe_lookup_name for safer string operations 2017-11-12 23:51:43 +11:00
kvm_emul.S
kvm.c powerpc/64: Fix watchdog configuration regressions 2017-08-31 14:26:00 +10:00
l2cr_6xx.S powerpc/l2cr_6xx: Fix invalid use of register expressions 2017-08-15 21:04:32 +10:00
legacy_serial.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
machine_kexec_32.c
machine_kexec_64.c powerpc/64s: Replace CONFIG_PPC_STD_MMU_64 with CONFIG_PPC_BOOK3S_64 2017-11-06 16:48:14 +11:00
machine_kexec_file_64.c resource: Provide resource struct in resource walk callback 2017-11-07 15:35:57 +01:00
machine_kexec.c powerpc: Update of_remove_property() call sites to remove null checking 2016-05-11 21:54:04 +10:00
Makefile powerpc updates for 4.15 2017-11-16 12:47:46 -08:00
mce_power.c powerpc/64s: Improve local TLB flush for boot and MCE on POWER9 2018-01-18 00:40:31 +11:00
mce.c powerpc updates for 4.16 2018-02-02 10:01:04 -08:00
misc_32.S powerpc/40x: Clear MSR_DR in one insn instead of two 2017-06-02 19:20:43 +10:00
misc_64.S powerpc/kexec: Fix kexec/kdump in P9 guest kernels 2017-11-24 16:49:37 +11:00
misc.S ppc: move exports to definitions 2016-08-07 23:50:09 -04:00
module_32.c powerpc/module: Only try to generate the ftrace_caller() stub once 2016-03-07 14:53:53 +11:00
module_64.c powerpc updates for 4.16 2018-02-02 10:01:04 -08:00
module.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
module.lds powerpc/modules: Fix alignment of .toc section in kernel modules 2017-12-11 13:03:35 +11:00
msi.c powerpc: Remove MSI-related PCI controller ops from ppc_md 2015-06-02 11:47:45 +10:00
nvram_64.c powerpc/nvram: use memdup_user 2017-06-27 17:02:50 -07:00
of_platform.c powerpc: Convert to using %pOF instead of full_name 2017-08-23 22:27:04 +10:00
optprobes_head.S powerpc/64: Rename soft_enabled to irq_soft_mask 2018-01-19 22:37:01 +11:00
optprobes.c powerpc/kprobes: Do not disable interrupts for optprobes and kprobes_on_ftrace 2017-11-12 23:51:41 +11:00
paca.c powerpc/64s: Relax PACA address limitations 2018-01-18 15:42:48 +11:00
pci_32.c powerpc/PCI: Deprecate pci_get_bus_and_slot() 2018-01-11 17:21:55 -06:00
pci_64.c powerpc/64s: Replace CONFIG_PPC_STD_MMU_64 with CONFIG_PPC_BOOK3S_64 2017-11-06 16:48:14 +11:00
pci_dn.c powerpc/pci: Separate SR-IOV Calls 2017-12-11 13:03:35 +11:00
pci_of_scan.c pci-v4.16-changes 2018-02-06 09:59:40 -08:00
pci-common.c pci-v4.16-fixes-1 2018-02-10 14:08:26 -08:00
pci-hotplug.c powerpc/pci: Unroll two pass loop when scanning bridges 2017-12-18 23:05:52 -06:00
pmc.c
ppc32.h
ppc_save_regs.S
proc_powerpc.c powerpc: Use octal numbers for file permissions 2018-01-22 05:48:33 +11:00
process.c powerpc updates for 4.16 2018-02-02 10:01:04 -08:00
prom_init_check.sh
prom_init.c powerpc: Enable support for ibm,drc-info devtree property 2018-01-21 16:21:50 +11:00
prom_parse.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
prom.c powerpc/mm: Separate ibm, dynamic-memory data from DT format 2018-01-16 23:26:27 +11:00
ptrace32.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
ptrace.c powerpc/ptrace: Add memory protection key regset 2018-01-20 22:59:06 +11:00
reloc_32.S
reloc_64.S powerpc/asm: Convert .llong directives to .8byte 2017-08-31 14:26:47 +10:00
rtas_flash.c powerpc: Use octal numbers for file permissions 2018-01-22 05:48:33 +11:00
rtas_pci.c powerpc/kernel: Change retrieval of pci_dn 2017-08-31 14:26:40 +10:00
rtas-proc.c powerpc: Use octal numbers for file permissions 2018-01-22 05:48:33 +11:00
rtas-rtc.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
rtas.c locking/arch, powerpc/rtas: Use arch_spin_lock() instead of arch_spin_lock_flags() 2017-10-18 15:15:07 +02:00
rtasd.c vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
setup_32.c powerpc/32: remove a NOP from memset() 2017-09-01 16:42:46 +10:00
setup_64.c powerpc/64s: Improve RFI L1-D cache flush fallback 2018-01-23 16:16:33 +11:00
setup-common.c powerpc updates for 4.16 2018-02-02 10:01:04 -08:00
setup.h powerpc/64s: Relax PACA address limitations 2018-01-18 15:42:48 +11:00
signal_32.c powerpc updates for 4.16 2018-02-02 10:01:04 -08:00
signal_64.c powerpc/tm: Fix endianness flip on trap 2018-01-22 05:48:36 +11:00
signal.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching 2018-01-31 13:02:18 -08:00
signal.h powerpc: tm: Rename transct_(*) to ck(\1)_state 2016-10-04 20:33:16 +11:00
smp-tbsync.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
smp.c powernv/kdump: Fix cases where the kdump kernel can get HMI's 2018-01-16 23:47:11 +11:00
stacktrace.c powerpc: Make /proc/self/stack always print the current stack 2017-03-28 14:43:59 +11:00
suspend.c
swsusp_32.S License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
swsusp_64.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/nmi.h> 2017-03-02 08:42:30 +01:00
swsusp_asm64.S powerpc: Fix invalid use of register expressions 2017-08-10 22:29:41 +10:00
swsusp_booke.S License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
swsusp.c powerpc/swsusp: Include suspend.h to silence sparse warnings 2017-03-20 19:02:49 +11:00
sys_ppc32.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
syscalls.c powerpc/tracing: Allow tracing of mmap syscalls 2017-04-12 22:32:43 +10:00
sysfs.c powerpc: Expose TSCR via sysfs 2018-01-22 05:48:36 +11:00
systbl_chk.c powerpc: Standardise on NR_syscalls rather than __NR_syscalls. 2015-11-26 22:11:17 +11:00
systbl_chk.sh powerpc: Standardise on NR_syscalls rather than __NR_syscalls. 2015-11-26 22:11:17 +11:00
systbl.S powerpc/asm: Convert .llong directives to .8byte 2017-08-31 14:26:47 +10:00
tau_6xx.c treewide: setup_timer() -> timer_setup() 2017-11-21 15:57:07 -08:00
time.c powerpc/64: Rename soft_enabled to irq_soft_mask 2018-01-19 22:37:01 +11:00
tm.S powerpc updates for 4.15 2017-11-16 12:47:46 -08:00
traps.c powerpc updates for 4.16 2018-02-02 10:01:04 -08:00
udbg_16550.c
udbg.c
uprobes.c powerpc/uprobes: Implement arch_uretprobe_is_alive() 2017-08-24 16:19:21 +10:00
vdso.c powerpc: Use feature bit for RTC presence rather than timebase presence 2018-03-24 00:36:45 +11:00
vecemu.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
vector.S License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
vmlinux.lds.S powerpc updates for 4.16 2018-02-02 10:01:04 -08:00
watchdog.c powerpc/watchdog: Print the NIP in soft_nmi_interrupt() 2018-01-28 17:08:29 +11:00