arch/arm64/kernel/paravirt.c

Source file repositories/reference/linux-study-clean/arch/arm64/kernel/paravirt.c

File Facts

System
Linux kernel
Corpus path
arch/arm64/kernel/paravirt.c
Extension
.c
Size
3598 bytes
Lines
168
Domain
Architecture Layer
Bucket
arch/arm64
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

struct pv_time_stolen_time_region {
	struct pvclock_vcpu_stolen_time __rcu *kaddr;
};

static DEFINE_PER_CPU(struct pv_time_stolen_time_region, stolen_time_region);

static bool steal_acc = true;
static int __init parse_no_stealacc(char *arg)
{
	steal_acc = false;
	return 0;
}

early_param("no-steal-acc", parse_no_stealacc);

/* return stolen time in ns by asking the hypervisor */
static u64 para_steal_clock(int cpu)
{
	struct pvclock_vcpu_stolen_time *kaddr = NULL;
	struct pv_time_stolen_time_region *reg;
	u64 ret = 0;

	reg = per_cpu_ptr(&stolen_time_region, cpu);

	/*
	 * paravirt_steal_clock() may be called before the CPU
	 * online notification callback runs. Until the callback
	 * has run we just return zero.
	 */
	rcu_read_lock();
	kaddr = rcu_dereference(reg->kaddr);
	if (!kaddr) {
		rcu_read_unlock();
		return 0;
	}

	ret = le64_to_cpu(READ_ONCE(kaddr->stolen_time));
	rcu_read_unlock();
	return ret;
}

static int stolen_time_cpu_down_prepare(unsigned int cpu)
{
	struct pvclock_vcpu_stolen_time *kaddr = NULL;
	struct pv_time_stolen_time_region *reg;

	reg = this_cpu_ptr(&stolen_time_region);
	if (!reg->kaddr)
		return 0;

	kaddr = rcu_replace_pointer(reg->kaddr, NULL, true);
	synchronize_rcu();
	memunmap(kaddr);

	return 0;
}

static int stolen_time_cpu_online(unsigned int cpu)
{
	struct pvclock_vcpu_stolen_time *kaddr = NULL;
	struct pv_time_stolen_time_region *reg;
	struct arm_smccc_res res;

	reg = this_cpu_ptr(&stolen_time_region);

	arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);

	if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
		return -EINVAL;

	kaddr = memremap(res.a0,
			      sizeof(struct pvclock_vcpu_stolen_time),
			      MEMREMAP_WB);

	rcu_assign_pointer(reg->kaddr, kaddr);

	if (!reg->kaddr) {
		pr_warn("Failed to map stolen time data structure\n");
		return -ENOMEM;
	}

	if (le32_to_cpu(kaddr->revision) != 0 ||
	    le32_to_cpu(kaddr->attributes) != 0) {
		pr_warn_once("Unexpected revision or attributes in stolen time data\n");
		return -ENXIO;
	}

	return 0;
}

Annotation

Implementation Notes