arm64: paravirt: Initialize steal time when cpu is online (75df529b) · Commits · 戴 / test

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: ("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>

arch/arm64/kernel/paravirt.c

+15 −11

Original line number	Diff line number	Diff line
		@@ -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(unsigned int cpu)
		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 int cpu)
		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;

include/linux/cpuhotplug.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -142,7 +142,6 @@ 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,

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