[RFC PATCH v2 21/23] KVM: arm64/sve: allow KVM_ARM_SVE_CONFIG_QUERY on vm fd

[Dave.Martin@arm.com (Dave Martin)]

Since userspace may need to decide on the set of vector lengths for
the guest before setting up a vm, it is onerous to require a vcpu
fd to be available first.  KVM_ARM_SVE_CONFIG_QUERY is not
vcpu-dependent anyway, so this patch wires up KVM_ARM_SVE_CONFIG to
be usable on a vm fd where appropriate.

Subcommands that are vcpu-dependent (currently
KVM_ARM_SVE_CONFIG_SET, KVM_ARM_SVE_CONFIG_GET) will return -EINVAL
if invoked on a vm fd.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
---
 arch/arm64/kvm/guest.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index f066b17..2313c22 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -574,6 +574,9 @@ static int kvm_vcpu_set_sve_vls(struct kvm_vcpu *vcpu, struct kvm_sve_vls *vls,
 	unsigned int vq, max_vq;
 	int ret;
 
+	if (!vcpu)
+		return -EINVAL; /* per-vcpu operation on vm fd */
+
 	if (vcpu->arch.has_run_once || vcpu_has_sve(vcpu))
 		return -EBADFD; /* too late, or already configured */
 
@@ -659,6 +662,9 @@ static int kvm_vcpu_query_sve_vls(struct kvm_vcpu *vcpu, struct kvm_sve_vls *vls
 static int kvm_vcpu_get_sve_vls(struct kvm_vcpu *vcpu, struct kvm_sve_vls *vls,
 		struct kvm_sve_vls __user *userp)
 {
+	if (!vcpu)
+		return -EINVAL; /* per-vcpu operation on vm fd */
+
 	if (!vcpu_has_sve(vcpu))
 		return -EBADFD; /* not configured yet */
 
@@ -668,6 +674,7 @@ static int kvm_vcpu_get_sve_vls(struct kvm_vcpu *vcpu, struct kvm_sve_vls *vls,
 			sve_vq_from_vl(vcpu->arch.sve_max_vl), userp);
 }
 
+/* vcpu may be NULL if this is called via a vm fd */
 static int kvm_vcpu_sve_config(struct kvm_vcpu *vcpu,
 			       struct kvm_sve_vls __user *userp)
 {
@@ -717,7 +724,15 @@ int kvm_arm_arch_vcpu_ioctl(struct kvm_vcpu *vcpu,
 int kvm_arm_arch_vm_ioctl(struct kvm *kvm,
 			  unsigned int ioctl, unsigned long arg)
 {
-	return -EINVAL;
+	void __user *userp = (void __user *)arg;
+
+	switch (ioctl) {
+	case KVM_ARM_SVE_CONFIG:
+		return kvm_vcpu_sve_config(NULL, userp);
+
+	default:
+		return -EINVAL;
+	}
 }
 
 int kvm_arch_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
-- 
2.1.4