KVM: ARM: Inject IRQs and FIQs from userspace

All interrupt injection is now based on the VM ioctl KVM_IRQ_LINE.  This
works semantically well for the GIC as we in fact raise/lower a line on
a machine component (the gic).  The IOCTL uses the follwing struct.

struct kvm_irq_level {
	union {
		__u32 irq;     /* GSI */
		__s32 status;  /* not used for KVM_IRQ_LEVEL */
	};
	__u32 level;           /* 0 or 1 */
};

ARM can signal an interrupt either at the CPU level, or at the in-kernel irqchip
(GIC), and for in-kernel irqchip can tell the GIC to use PPIs designated for
specific cpus.  The irq field is interpreted like this:

  bits:  | 31 ... 24 | 23  ... 16 | 15    ...    0 |
  field: | irq_type  | vcpu_index |   irq_number   |

The irq_type field has the following values:
- irq_type[0]: out-of-kernel GIC: irq_number 0 is IRQ, irq_number 1 is FIQ
- irq_type[1]: in-kernel GIC: SPI, irq_number between 32 and 1019 (incl.)
               (the vcpu_index field is ignored)
- irq_type[2]: in-kernel GIC: PPI, irq_number between 16 and 31 (incl.)

The irq_number thus corresponds to the irq ID in as in the GICv2 specs.

This is documented in Documentation/kvm/api.txt.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>

arch/arm/kvm/arm.c

@@ -24,6 +24,7 @@
 #include <linux/fs.h>
 #include <linux/mman.h>
 #include <linux/sched.h>
+#include <linux/kvm.h>
 #include <trace/events/kvm.h>
 
 #define CREATE_TRACE_POINTS
@@ -284,6 +285,7 @@ void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu)
 
 void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
+	vcpu->cpu = cpu;
 }
 
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
@@ -319,6 +321,69 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 	return -EINVAL;
 }
 
+static int vcpu_interrupt_line(struct kvm_vcpu *vcpu, int number, bool level)
+{
+	int bit_index;
+	bool set;
+	unsigned long *ptr;
+
+	if (number == KVM_ARM_IRQ_CPU_IRQ)
+		bit_index = __ffs(HCR_VI);
+	else /* KVM_ARM_IRQ_CPU_FIQ */
+		bit_index = __ffs(HCR_VF);
+
+	ptr = (unsigned long *)&vcpu->arch.irq_lines;
+	if (level)
+		set = test_and_set_bit(bit_index, ptr);
+	else
+		set = test_and_clear_bit(bit_index, ptr);
+
+	/*
+	 * If we didn't change anything, no need to wake up or kick other CPUs
+	 */
+	if (set == level)
+		return 0;
+
+	/*
+	 * The vcpu irq_lines field was updated, wake up sleeping VCPUs and
+	 * trigger a world-switch round on the running physical CPU to set the
+	 * virtual IRQ/FIQ fields in the HCR appropriately.
+	 */
+	kvm_vcpu_kick(vcpu);
+
+	return 0;
+}
+
+int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level)
+{
+	u32 irq = irq_level->irq;
+	unsigned int irq_type, vcpu_idx, irq_num;
+	int nrcpus = atomic_read(&kvm->online_vcpus);
+	struct kvm_vcpu *vcpu = NULL;
+	bool level = irq_level->level;
+
+	irq_type = (irq >> KVM_ARM_IRQ_TYPE_SHIFT) & KVM_ARM_IRQ_TYPE_MASK;
+	vcpu_idx = (irq >> KVM_ARM_IRQ_VCPU_SHIFT) & KVM_ARM_IRQ_VCPU_MASK;
+	irq_num = (irq >> KVM_ARM_IRQ_NUM_SHIFT) & KVM_ARM_IRQ_NUM_MASK;
+
+	trace_kvm_irq_line(irq_type, vcpu_idx, irq_num, irq_level->level);
+
+	if (irq_type != KVM_ARM_IRQ_TYPE_CPU)
+		return -EINVAL;
+
+	if (vcpu_idx >= nrcpus)
+		return -EINVAL;
+
+	vcpu = kvm_get_vcpu(kvm, vcpu_idx);
+	if (!vcpu)
+		return -EINVAL;
+
+	if (irq_num > KVM_ARM_IRQ_CPU_FIQ)
+		return -EINVAL;
+
+	return vcpu_interrupt_line(vcpu, irq_num, level);
+}
+
 long kvm_arch_vcpu_ioctl(struct file *filp,
 			 unsigned int ioctl, unsigned long arg)
 {