From: Andrew Jones drjones@redhat.com
commit 75df529bec9110dad43ab30e2d9490242529e8b8 upstream.
Steal time initialization requires mapping a memory region which invokes a memory allocation. Doing this at CPU starting time results in the following trace when CONFIG_DEBUG_ATOMIC_SLEEP is enabled:
BUG: sleeping function called from invalid context at mm/slab.h:498 in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 0, name: swapper/1 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.9.0-rc5+ #1 Call trace: dump_backtrace+0x0/0x208 show_stack+0x1c/0x28 dump_stack+0xc4/0x11c ___might_sleep+0xf8/0x130 __might_sleep+0x58/0x90 slab_pre_alloc_hook.constprop.101+0xd0/0x118 kmem_cache_alloc_node_trace+0x84/0x270 __get_vm_area_node+0x88/0x210 get_vm_area_caller+0x38/0x40 __ioremap_caller+0x70/0xf8 ioremap_cache+0x78/0xb0 memremap+0x9c/0x1a8 init_stolen_time_cpu+0x54/0xf0 cpuhp_invoke_callback+0xa8/0x720 notify_cpu_starting+0xc8/0xd8 secondary_start_kernel+0x114/0x180 CPU1: Booted secondary processor 0x0000000001 [0x431f0a11]
However we don't need to initialize steal time at CPU starting time. We can simply wait until CPU online time, just sacrificing a bit of accuracy by returning zero for steal time until we know better.
While at it, add __init to the functions that are only called by pv_time_init() which is __init.
Signed-off-by: Andrew Jones drjones@redhat.com Fixes: e0685fa228fd ("arm64: Retrieve stolen time as paravirtualized guest") Cc: stable@vger.kernel.org Reviewed-by: Steven Price steven.price@arm.com Link: https://lore.kernel.org/r/20200916154530.40809-1-drjones@redhat.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm64/kernel/paravirt.c | 26 +++++++++++++++----------- include/linux/cpuhotplug.h | 1 - 2 files changed, 15 insertions(+), 12 deletions(-)
--- a/arch/arm64/kernel/paravirt.c +++ b/arch/arm64/kernel/paravirt.c @@ -50,16 +50,19 @@ static u64 pv_steal_clock(int cpu) struct pv_time_stolen_time_region *reg;
reg = per_cpu_ptr(&stolen_time_region, cpu); - if (!reg->kaddr) { - pr_warn_once("stolen time enabled but not configured for cpu %d\n", - cpu); + + /* + * paravirt_steal_clock() may be called before the CPU + * online notification callback runs. Until the callback + * has run we just return zero. + */ + if (!reg->kaddr) return 0; - }
return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time)); }
-static int stolen_time_dying_cpu(unsigned int cpu) +static int stolen_time_cpu_down_prepare(unsigned int cpu) { struct pv_time_stolen_time_region *reg;
@@ -73,7 +76,7 @@ static int stolen_time_dying_cpu(unsigne return 0; }
-static int init_stolen_time_cpu(unsigned int cpu) +static int stolen_time_cpu_online(unsigned int cpu) { struct pv_time_stolen_time_region *reg; struct arm_smccc_res res; @@ -103,19 +106,20 @@ static int init_stolen_time_cpu(unsigned return 0; }
-static int pv_time_init_stolen_time(void) +static int __init pv_time_init_stolen_time(void) { int ret;
- ret = cpuhp_setup_state(CPUHP_AP_ARM_KVMPV_STARTING, - "hypervisor/arm/pvtime:starting", - init_stolen_time_cpu, stolen_time_dying_cpu); + ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, + "hypervisor/arm/pvtime:online", + stolen_time_cpu_online, + stolen_time_cpu_down_prepare); if (ret < 0) return ret; return 0; }
-static bool has_pv_steal_clock(void) +static bool __init has_pv_steal_clock(void) { struct arm_smccc_res res;
--- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -141,7 +141,6 @@ enum cpuhp_state { /* Must be the last timer callback */ CPUHP_AP_DUMMY_TIMER_STARTING, CPUHP_AP_ARM_XEN_STARTING, - CPUHP_AP_ARM_KVMPV_STARTING, CPUHP_AP_ARM_CORESIGHT_STARTING, CPUHP_AP_ARM_CORESIGHT_CTI_STARTING, CPUHP_AP_ARM64_ISNDEP_STARTING,