[PATCH] KVM: Get rid of return value from kvm_arch_create_vm_debugfs()

Oliver Upton
2024-02-16T16:00:01Z

The general expectation with debugfs is that any initialization failure
is nonfatal. Nevertheless, kvm_arch_create_vm_debugfs() allows
implementations to return an error and kvm_create_vm_debugfs() allows
that to fail VM creation.

Change to a void return to discourage architectures from making debugfs
failures fatal for the VM. Seems like everyone already had the right
idea, as all implementations already return 0 unconditionally.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---

Compile-tested on arm64, powerpc, and x86 since I don't trust myself to
even get this simple patch right.

arch/powerpc/kvm/powerpc.c | 3 +--
arch/x86/kvm/debugfs.c | 3 +--
include/linux/kvm_host.h | 2 +-
virt/kvm/kvm_main.c | 8 ++------
4 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 23407fbd73c9..d32abe7fe6ab 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -2538,9 +2538,8 @@ void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu, struct dentry *debugfs_
vcpu->kvm->arch.kvm_ops->create_vcpu_debugfs(vcpu, debugfs_dentry);
}

-int kvm_arch_create_vm_debugfs(struct kvm *kvm)
+void kvm_arch_create_vm_debugfs(struct kvm *kvm)
{
if (kvm->arch.kvm_ops->create_vm_debugfs)
kvm->arch.kvm_ops->create_vm_debugfs(kvm);
- return 0;
}
diff --git a/arch/x86/kvm/debugfs.c b/arch/x86/kvm/debugfs.c
index 95ea1a1f7403..999227fc7c66 100644
--- a/arch/x86/kvm/debugfs.c
+++ b/arch/x86/kvm/debugfs.c
@@ -189,9 +189,8 @@ static const struct file_operations mmu_rmaps_stat_fops = {
.release = kvm_mmu_rmaps_stat_release,
};

-int kvm_arch_create_vm_debugfs(struct kvm *kvm)
+void kvm_arch_create_vm_debugfs(struct kvm *kvm)
{
debugfs_create_file("mmu_rmaps_stat", 0644, kvm->debugfs_dentry, kvm,
&mmu_rmaps_stat_fops);
- return 0;
}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7e7fd25b09b3..9a45f673f687 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1507,7 +1507,7 @@ bool kvm_arch_dy_runnable(struct kvm_vcpu *vcpu);
bool kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu);
int kvm_arch_post_init_vm(struct kvm *kvm);
void kvm_arch_pre_destroy_vm(struct kvm *kvm);
-int kvm_arch_create_vm_debugfs(struct kvm *kvm);
+void kvm_arch_create_vm_debugfs(struct kvm *kvm);

#ifndef __KVM_HAVE_ARCH_VM_ALLOC
/*
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 10bfc88a69f7..c681149c382a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1150,10 +1150,7 @@ static int kvm_create_vm_debugfs(struct kvm *kvm, const char *fdname)
&stat_fops_per_vm);
}

- ret = kvm_arch_create_vm_debugfs(kvm);
- if (ret)
- goto out_err;
-
+ kvm_arch_create_vm_debugfs(kvm);
return 0;
out_err:
kvm_destroy_vm_debugfs(kvm);
@@ -1183,9 +1180,8 @@ void __weak kvm_arch_pre_destroy_vm(struct kvm *kvm)
* Cleanup should be automatic done in kvm_destroy_vm_debugfs() recursively, so
* a per-arch destroy interface is not needed.
*/
-int __weak kvm_arch_create_vm_debugfs(struct kvm *kvm)
+void __weak kvm_arch_create_vm_debugfs(struct kvm *kvm)
{
- return 0;
}

static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)

base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
--
2.44.0.rc0.258.g7320e95886-goog