KVM: arm64: Always return generic v8 as the preferred target

Userspace selecting an implementation-specific vCPU target has been
completely useless for a very long time. Let's go whole hog and start
returning the generic v8 target across all implementations as the
preferred target.

Uphold the pre-existing behavior by tolerating either the generic target
or an implementation-specific target if the vCPU happens to be running
on one of the lucky few parts.

Acked-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230710193140.1706399-5-oliver.upton@linux.dev

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index b53105b..ed60277 100644 (file)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -898,7 +898,6 @@ struct kvm_vcpu_stat {
        u64 exits;
 };
 
-void kvm_vcpu_preferred_target(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);
 int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 13f1bde..9ab17ec 100644 (file)
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1250,7 +1250,8 @@ static int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
 {
        int ret;
 
-       if (init->target != kvm_target_cpu())
+       if (init->target != KVM_ARM_TARGET_GENERIC_V8 &&
+           init->target != kvm_target_cpu())
                return -EINVAL;
 
        ret = kvm_vcpu_init_check_features(vcpu, init);
@@ -1585,9 +1586,9 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
                return kvm_vm_ioctl_set_device_addr(kvm, &dev_addr);
        }
        case KVM_ARM_PREFERRED_TARGET: {
-               struct kvm_vcpu_init init;
-
-               kvm_vcpu_preferred_target(&init);
+               struct kvm_vcpu_init init = {
+                       .target = KVM_ARM_TARGET_GENERIC_V8,
+               };
 
                if (copy_to_user(argp, &init, sizeof(init)))
                        return -EFAULT;

diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 20280a5..95f6945 100644 (file)
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -884,21 +884,6 @@ u32 __attribute_const__ kvm_target_cpu(void)
        return KVM_ARM_TARGET_GENERIC_V8;
 }
 
-void kvm_vcpu_preferred_target(struct kvm_vcpu_init *init)
-{
-       u32 target = kvm_target_cpu();
-
-       memset(init, 0, sizeof(*init));
-
-       /*
-        * For now, we don't return any features.
-        * In future, we might use features to return target
-        * specific features available for the preferred
-        * target type.
-        */
-       init->target = (__u32)target;
-}
-
 int kvm_arch_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
 {
        return -EINVAL;