KVM: arm64: Add initial support for KVM_CAP_EXIT_HYPERCALL
Allow the VMM to hook into and handle a subset of guest hypercalls
advertised by the host. For now, no such hypercalls exist, and so the
new capability returns 0 when queried.
Signed-off-by: Will Deacon <will@kernel.org>
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index d3ea09c..d1c198c 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -208,6 +208,8 @@
u8 pfr0_csv3;
struct kvm_protected_vm pkvm;
+
+ u64 hypercall_exit_enabled;
};
struct kvm_protected_vcpu {
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 94dad60..75c57f8 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -59,6 +59,9 @@
static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
DEFINE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
+/* KVM "vendor" hypercalls which may be forwarded to userspace on request. */
+#define KVM_EXIT_HYPERCALL_VALID_MASK (0)
+
int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
{
return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
@@ -98,6 +101,19 @@
}
mutex_unlock(&kvm->lock);
break;
+ case KVM_CAP_EXIT_HYPERCALL:
+ if (cap->flags)
+ return -EINVAL;
+
+ if (cap->args[0] & ~KVM_EXIT_HYPERCALL_VALID_MASK)
+ return -EINVAL;
+
+ if (cap->args[1] || cap->args[2] || cap->args[3])
+ return -EINVAL;
+
+ WRITE_ONCE(kvm->arch.hypercall_exit_enabled, cap->args[0]);
+ r = 0;
+ break;
default:
r = -EINVAL;
break;
@@ -297,6 +313,9 @@
case KVM_CAP_ARM_PTRAUTH_GENERIC:
r = system_has_full_ptr_auth();
break;
+ case KVM_CAP_EXIT_HYPERCALL:
+ r = KVM_EXIT_HYPERCALL_VALID_MASK;
+ break;
default:
r = 0;
}
@@ -865,6 +884,12 @@
ret = kvm_handle_mmio_return(vcpu);
if (ret)
return ret;
+ } else if (run->exit_reason == KVM_EXIT_HYPERCALL) {
+ smccc_set_retval(vcpu,
+ vcpu->run->hypercall.ret,
+ vcpu->run->hypercall.args[0],
+ vcpu->run->hypercall.args[1],
+ vcpu->run->hypercall.args[2]);
}
vcpu_load(vcpu);
diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
index 30da78f..e41571f 100644
--- a/arch/arm64/kvm/hypercalls.c
+++ b/arch/arm64/kvm/hypercalls.c
@@ -58,6 +58,24 @@
val[3] = lower_32_bits(cycles);
}
+static int kvm_vcpu_exit_hcall(struct kvm_vcpu *vcpu, u32 nr, u32 nr_args)
+{
+ u64 mask = vcpu->kvm->arch.hypercall_exit_enabled;
+ u32 i;
+
+ if (nr_args > 6 || !(mask & BIT(nr)))
+ return -EINVAL;
+
+ vcpu->run->exit_reason = KVM_EXIT_HYPERCALL;
+ vcpu->run->hypercall.nr = nr;
+
+ for (i = 0; i < nr_args; ++i)
+ vcpu->run->hypercall.args[i] = vcpu_get_reg(vcpu, i + 1);
+
+ vcpu->run->hypercall.longmode = !vcpu_mode_is_32bit(vcpu);
+ return 0;
+}
+
int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
{
u32 func_id = smccc_get_function(vcpu);
