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fcec538ef8
linux/arch/mips/kernel
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Hauke Mehrtens fcec538ef8 MIPS: Add missing EHB in mtc0 -> mfc0 sequence for DSPen 
This resolves the hazard between the mtc0 in the change_c0_status() and
the mfc0 in configure_exception_vector(). Without resolving this hazard
configure_exception_vector() could read an old value and would restore
this old value again. This would revert the changes change_c0_status()
did. I checked this by printing out the read_c0_status() at the end of
per_cpu_trap_init() and the ST0_MX is not set without this patch.

The hazard is documented in the MIPS Architecture Reference Manual Vol.
III: MIPS32/microMIPS32 Privileged Resource Architecture (MD00088), rev
6.03 table 8.1 which includes:

   Producer | Consumer | Hazard
  ----------|----------|----------------------------
   mtc0     | mfc0     | any coprocessor 0 register

I saw this hazard on an Atheros AR9344 rev 2 SoC with a MIPS 74Kc CPU.
There the change_c0_status() function would activate the DSPen by
setting ST0_MX in the c0_status register. This was reverted and then the
system got a DSP exception when the DSP registers were saved in
save_dsp() in the first process switch. The crash looks like this:

[    0.089999] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.097796] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.107070] Kernel panic - not syncing: Unexpected DSP exception
[    0.113470] Rebooting in 1 seconds..

We saw this problem in OpenWrt only on the MIPS 74Kc based Atheros SoCs,
not on the 24Kc based SoCs. We only saw it with kernel 5.4 not with
kernel 4.19, in addition we had to use GCC 8.4 or 9.X, with GCC 8.3 it
did not happen.

In the kernel I bisected this problem to commit 9012d01166 ("compiler:
allow all arches to enable CONFIG_OPTIMIZE_INLINING"), but when this was
reverted it also happened after commit 172dcd935c ("MIPS: Always
allocate exception vector for MIPSr2+").

Commit 0b24cae4d5 ("MIPS: Add missing EHB in mtc0 -> mfc0 sequence.")
does similar changes to a different file. I am not sure if there are
more places affected by this problem.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
2020-07-05 11:43:25 +02:00
..
syscalls vfs: add faccessat2 syscall 2020-05-14 16:44:25 +02:00
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
asm-offsets.c MIPS: Remove struct task_struct fpu state when CONFIG_MIPS_FP_SUPPORT=n 2018-11-09 10:23:19 -08:00
binfmt_elfn32.c y2038: elfcore: Use __kernel_old_timeval for process times 2019-11-15 14:38:29 +01:00
binfmt_elfo32.c y2038: elfcore: Use __kernel_old_timeval for process times 2019-11-15 14:38:29 +01:00
bmips_5xxx_init.S MIPS: BCM5xxx: Remove dead init_fpu code 2018-11-08 11:20:57 -08:00
bmips_vec.S MIPS: BMIPS: Add Whirlwind (BMIPS5200) initialization code 2016-05-09 12:00:01 +02:00
branch.c MIPS: Use fallthrough for arch/mips 2020-05-07 11:55:47 +02:00
cacheinfo.c mips: cacheinfo: report shared CPU map 2019-11-26 10:33:08 -08:00
cevt-bcm1480.c MIPS: Replace setup_irq() by request_irq() 2020-03-05 16:47:35 +01:00
cevt-ds1287.c MIPS: Replace setup_irq() by request_irq() 2020-03-05 16:47:35 +01:00
cevt-gt641xx.c MIPS: Replace setup_irq() by request_irq() 2020-03-05 16:47:35 +01:00
cevt-r4k.c mips: cevt-r4k: Update the r4k-clockevent frequency in sync with CPU 2020-05-22 09:14:32 +02:00
cevt-sb1250.c MIPS: Replace setup_irq() by request_irq() 2020-03-05 16:47:35 +01:00
cevt-txx9.c MIPS: Replace setup_irq() by request_irq() 2020-03-05 16:47:35 +01:00
cmpxchg.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
cps-vec-ns16550.S mips: Add CPS_NS16550_WIDTH config 2020-05-22 09:12:52 +02:00
cps-vec.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
cpu-probe.c KVM: MIPS: Enable KVM support for Loongson-3 2020-06-04 13:51:53 -04:00
crash_dump.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
crash.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
csrc-bcm1480.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
csrc-ioasic.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
csrc-r4k.c mips: csrc-r4k: Mark R4K timer as unstable if CPU freq changes 2020-05-22 09:14:06 +02:00
csrc-sb1250.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
early_printk_8250.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 1 2019-05-21 11:28:39 +02:00
early_printk.c mips: unify prom_putchar() declarations 2018-07-17 09:40:17 -07:00
elf.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
entry.S mips: Add MIPS Release 5 support 2020-05-22 09:09:01 +02:00
ftrace.c MIPS: ftrace: Reword prepare_ftrace_return() comment block 2019-06-11 15:46:21 -07:00
genex.S MIPS: Fix IRQ tracing when call handle_fpe() and handle_msa_fpe() 2020-05-27 13:11:49 +02:00
gpio_txx9.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
head.S MIPS: Clear XContext at boot time 2020-04-24 18:37:23 +02:00
i8253.c MIPS: Replace setup_irq() by request_irq() 2020-03-05 16:47:35 +01:00
idle.c MIPS: Use fallthrough for arch/mips 2020-05-07 11:55:47 +02:00
irq_txx9.c
irq-gt641xx.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 1 2019-05-21 11:28:39 +02:00
irq-msc01.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
irq-rm7000.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
irq.c MIPS: irq: Allocate accurate order pages for irq stack 2019-02-19 12:45:01 -08:00
jump_label.c MIPS: jump_label: Use compact branches for >= r6 2019-04-09 16:21:30 -07:00
kgdb.c MIPS: KGDB: fix kgdb support for SMP platforms. 2019-03-28 11:35:58 -07:00
kprobes.c mm, kprobes: generalize and rename notify_page_fault() as kprobe_page_fault() 2019-07-16 19:23:22 -07:00
linux32.c MIPS: Delete unused code in linux32.c 2018-08-01 13:20:27 -07:00
machine_kexec.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 230 2019-06-19 17:09:06 +02:00
Makefile MIPS: Remove not used 8250-platform.c 2020-05-17 10:25:26 +02:00
mcount.S mips: ftrace: fix static function graph tracing 2018-06-19 15:00:12 -07:00
mips_machine.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
mips-cm.c mips: cm: Add L2 ECC/parity errors reporting 2020-05-07 13:11:38 +02:00
mips-cpc.c remove ioremap_nocache and devm_ioremap_nocache 2020-01-06 09:45:59 +01:00
mips-mt-fpaff.c sched/core: Provide a pointer to the valid CPU mask 2019-06-03 11:49:37 +02:00
mips-mt.c MIPS: MT: Remove norps command line parameter 2018-11-26 22:49:14 -08:00
mips-r2-to-r6-emul.c MIPS: Use fallthrough for arch/mips 2020-05-07 11:55:47 +02:00
module.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
octeon_switch.S Kbuild: rename CC_STACKPROTECTOR[_STRONG] config variables 2018-06-14 12:21:18 +09:00
perf_event_mipsxx.c MIPS: perf: Remove unnecessary "fallthrough" pseudo keywords 2020-05-02 13:21:09 +02:00
perf_event.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
pm-cps.c MIPS: barrier: Add __SYNC() infrastructure 2019-10-07 09:42:17 -07:00
pm.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
probes-common.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
proc.c mips: Add MIPS Release 5 support 2020-05-22 09:09:01 +02:00
process.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
prom.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
ptrace32.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
ptrace.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
r4k_fpu.S mips: Add MIPS Release 5 support 2020-05-22 09:09:01 +02:00
r4k_switch.S Kbuild: rename CC_STACKPROTECTOR[_STRONG] config variables 2018-06-14 12:21:18 +09:00
r4k-bugs64.c MIPS: r4k-bugs64: Drop CONFIG_CPU_MIPSR6 checks 2019-10-07 09:38:54 -07:00
r2300_fpu.S MIPS: Simplify FP context initialization 2018-11-09 10:23:13 -08:00
r2300_switch.S Kbuild: rename CC_STACKPROTECTOR[_STRONG] config variables 2018-06-14 12:21:18 +09:00
relocate_kernel.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 230 2019-06-19 17:09:06 +02:00
relocate.c MIPS: Remove no-op/identity casts 2018-08-31 11:49:20 -07:00
reset.c MIPS: Hang more efficiently on halt/powerdown/restart 2018-03-09 11:22:43 +00:00
rtlx-cmp.c
rtlx-mt.c MIPS: Replace setup_irq() by request_irq() 2020-03-05 16:47:35 +01:00
rtlx.c vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
scall32-o32.S mips: remove nargs from __SYSCALL 2019-07-30 10:50:30 -07:00
scall64-n32.S mips: remove nargs from __SYSCALL 2019-07-30 10:50:30 -07:00
scall64-n64.S mips: remove nargs from __SYSCALL 2019-07-30 10:50:30 -07:00
scall64-o32.S MIPS: asm: Rename some macros to avoid build errors 2020-05-07 13:20:05 +02:00
segment.c mips: kernel: no need to check return value of debugfs_create functions 2019-01-22 11:17:20 -08:00
setup.c MIPS: Remove useless parameter of bootcmdline_init() 2020-05-19 17:36:04 +02:00
signal32.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
signal_n32.c Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2019-07-08 21:48:15 -07:00
signal_o32.c signal: Remove task parameter from force_sig 2019-05-27 09:36:28 -05:00
signal-common.h
signal.c MIPS: Replace zero-length array with flexible-array 2020-05-08 12:01:02 +02:00
smp-bmips.c mm: don't include asm/pgtable.h if linux/mm.h is already included 2020-06-09 09:39:13 -07:00
smp-cmp.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 182 2019-05-30 11:29:20 -07:00
smp-cps.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
smp-mt.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 182 2019-05-30 11:29:20 -07:00
smp-up.c MIPS: SMP: Allow boot_secondary SMP op to return errors 2017-08-30 00:57:27 +02:00
smp.c MIPS updates for v5.7: 2020-03-31 08:51:45 -07:00
spinlock_test.c mips: kernel: no need to check return value of debugfs_create functions 2019-01-22 11:17:20 -08:00
spram.c mips: Add CONFIG/CONFIG6/Cause reg fields macro 2020-05-22 09:12:22 +02:00
stacktrace.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
sync-r4k.c MIPS: sync-r4k: do slave counter synchronization with disabled HW interrupts 2020-01-22 10:16:18 -08:00
syscall.c MIPS: syscall: Emit Loongson3 sync workarounds within asm 2019-10-07 09:43:05 -07:00
sysrq.c MIPS: constify sysrq_key_op 2020-05-15 14:53:19 +02:00
time.c mips: Add udelay lpj numbers adjustment 2020-05-22 09:13:32 +02:00
topology.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
traps.c MIPS: Add missing EHB in mtc0 -> mfc0 sequence for DSPen 2020-07-05 11:43:25 +02:00
unaligned.c MIPS: Fix build warning about "PTR_STR" redefinition 2020-05-30 10:58:30 +02:00
uprobes.c MIPS: uprobes: remove set but not used variable 'epc' 2019-05-29 13:20:30 -07:00
vdso.c mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
vmlinux.lds.S MIPS: Truncate link address into 32bit for 32bit kernel 2020-05-07 10:31:01 +02:00
vpe-cmp.c
vpe-mt.c
vpe.c MIPS: VPE: Fix a double free and a memory leak in 'release_vpe()' 2020-02-15 12:44:03 -08:00
watch.c MIPS: Use fallthrough for arch/mips 2020-05-07 11:55:47 +02:00