Michael Ellerman 56376c5864 powerpc/kvm: Fix lockups when running KVM guests on Power8 ... When running KVM guests on Power8 we can see a lockup where one CPU stops responding. This often leads to a message such as: watchdog: CPU 136 detected hard LOCKUP on other CPUs 72 Task dump for CPU 72: qemu-system-ppc R running task 10560 20917 20908 0x00040004 And then backtraces on other CPUs, such as: Task dump for CPU 48: ksmd R running task 10032 1519 2 0x00000804 Call Trace: ... --- interrupt: 901 at smp_call_function_many+0x3c8/0x460 LR = smp_call_function_many+0x37c/0x460 pmdp_invalidate+0x100/0x1b0 __split_huge_pmd+0x52c/0xdb0 try_to_unmap_one+0x764/0x8b0 rmap_walk_anon+0x15c/0x370 try_to_unmap+0xb4/0x170 split_huge_page_to_list+0x148/0xa30 try_to_merge_one_page+0xc8/0x990 try_to_merge_with_ksm_page+0x74/0xf0 ksm_scan_thread+0x10ec/0x1ac0 kthread+0x160/0x1a0 ret_from_kernel_thread+0x5c/0x78 This is caused by commit 8c1c7fb0b5 ("powerpc/64s/idle: avoid sync for KVM state when waking from idle"), which added a check in pnv_powersave_wakeup() to see if the kvm_hstate.hwthread_state is already set to KVM_HWTHREAD_IN_KERNEL, and if so to skip the store and test of kvm_hstate.hwthread_req. The problem is that the primary does not set KVM_HWTHREAD_IN_KVM when entering the guest, so it can then come out to cede with KVM_HWTHREAD_IN_KERNEL set. It can then go idle in kvm_do_nap after setting hwthread_req to 1, but because hwthread_state is still KVM_HWTHREAD_IN_KERNEL we will skip the test of hwthread_req when we wake up from idle and won't go to kvm_start_guest. From there the thread will return somewhere garbage and crash. Fix it by skipping the store of hwthread_state, but not the test of hwthread_req, when coming out of idle. It's OK to skip the sync in that case because hwthread_req will have been set on the same thread, so there is no synchronisation required. Fixes: 8c1c7fb0b5 ("powerpc/64s/idle: avoid sync for KVM state when waking from idle") Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>		2018-04-19 16:22:20 +10:00
..
boot	powerpc updates for 4.17	2018-04-07 12:08:19 -07:00
configs	scsi: remove the fdomain and fdomain_cs drivers	2018-03-19 22:54:47 -04:00
crypto	crypto: hash - annotate algorithms taking optional key	2018-01-12 23:03:35 +11:00
include	powerpc fixes for 4.17 #2	2018-04-15 11:57:12 -07:00
kernel	powerpc/kvm: Fix lockups when running KVM guests on Power8	2018-04-19 16:22:20 +10:00
kvm	powerpc fixes for 4.17 #2	2018-04-15 11:57:12 -07:00
lib	powerpc/lib: Fix off-by-one in alternate feature patching	2018-04-17 00:37:48 +10:00
math-emu	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
mm	powerpc fixes for 4.17 #2	2018-04-15 11:57:12 -07:00
net	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2018-03-05 11:29:24 -08:00
oprofile	powerpc: Use sizeof(*foo) rather than sizeof(struct foo)	2018-03-20 16:47:53 +11:00
perf	powerpc updates for 4.17	2018-04-07 12:08:19 -07:00
platforms	powerpc fixes for 4.17 #2	2018-04-15 11:57:12 -07:00
purgatory	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
sysdev	powerpc/xive: Fix trying to "push" an already active pool VP	2018-04-19 00:49:45 +10:00
tools	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
xmon	Merge branch 'topic/paca' into next	2018-03-31 09:09:36 +11:00
Kconfig	kexec_file: make use of purgatory optional	2018-04-13 17:10:27 -07:00
Kconfig.debug	powerpc: Add new kconfig CONFIG_PPC_IRQ_SOFT_MASK_DEBUG	2018-01-19 22:37:03 +11:00
Makefile	powerpc/64s: Add POWER9 CPU type selection	2018-04-01 22:15:32 +10:00
Makefile.postlink	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00