[RFC PATCH 1/3] ARM: KVM: Implement target CPU=Host

[Anup Patel <anup.patel@xxxxxxxxxx>]

This patch implements KVM_ARM_TARGET_HOST for KVM ARM.

If user space provides KVM_ARM_TARGET_HOST as target type in
KVM_ARM_VCPU_INIT ioctl then we find out appropriate target
type based on underlying host and return that to user space
via struct kvm_vcpu_init.

Signed-off-by: Anup Patel <anup.patel@xxxxxxxxxx>
Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@xxxxxxxxxx>
---
 arch/arm/include/asm/kvm_host.h |    2 +-
 arch/arm/include/uapi/asm/kvm.h |    1 +
 arch/arm/kvm/arm.c              |    9 ++++++++-
 arch/arm/kvm/guest.c            |   11 +++++++++--
 4 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 7d22517..3bb6c2b 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -153,7 +153,7 @@ struct kvm_vcpu_stat {
 
 struct kvm_vcpu_init;
 int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
-			const struct kvm_vcpu_init *init);
+			struct kvm_vcpu_init *init);
 unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu);
 int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);
 struct kvm_one_reg;
diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
index c1ee007..644012e 100644
--- a/arch/arm/include/uapi/asm/kvm.h
+++ b/arch/arm/include/uapi/asm/kvm.h
@@ -63,6 +63,7 @@ struct kvm_regs {
 
 /* Supported Processor Types */
 #define KVM_ARM_TARGET_CORTEX_A15	0
+#define KVM_ARM_TARGET_HOST		0x0FFFFFFF
 #define KVM_ARM_NUM_TARGETS		1
 
 /* KVM_ARM_SET_DEVICE_ADDR ioctl id encoding */
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 741f66a..d8e494e 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -698,6 +698,7 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level,
 long kvm_arch_vcpu_ioctl(struct file *filp,
 			 unsigned int ioctl, unsigned long arg)
 {
+	int err;
 	struct kvm_vcpu *vcpu = filp->private_data;
 	void __user *argp = (void __user *)arg;
 
@@ -708,8 +709,14 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		if (copy_from_user(&init, argp, sizeof(init)))
 			return -EFAULT;
 
-		return kvm_vcpu_set_target(vcpu, &init);
+		err = kvm_vcpu_set_target(vcpu, &init);
+		if (err)
+			return err;
+
+		if (copy_to_user(argp, &init, sizeof(init)))
+			return -EFAULT;
 
+		return 0;
 	}
 	case KVM_SET_ONE_REG:
 	case KVM_GET_ONE_REG: {
diff --git a/arch/arm/kvm/guest.c b/arch/arm/kvm/guest.c
index 152d036..050df63 100644
--- a/arch/arm/kvm/guest.c
+++ b/arch/arm/kvm/guest.c
@@ -198,12 +198,19 @@ int __attribute_const__ kvm_target_cpu(void)
 }
 
 int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
-			const struct kvm_vcpu_init *init)
+			struct kvm_vcpu_init *init)
 {
 	unsigned int i;
+	int phys_target = kvm_target_cpu();
+
+	if (phys_target < 0) {
+		return phys_target;
+	}
 
 	/* We can only do a cortex A15 for now. */
-	if (init->target != kvm_target_cpu())
+	if (init->target == KVM_ARM_TARGET_HOST)
+		init->target = phys_target;
+	else if (init->target != phys_target)
 		return -EINVAL;
 
 	vcpu->arch.target = init->target;
-- 
1.7.9.5

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