Re: [PATCH 4/5] KVM: Actually create debugfs in kvm_create_vm()

[Sean Christopherson <seanjc@google.com>]

On Fri, Apr 15, 2022, Oliver Upton wrote:
> @@ -1049,7 +1050,7 @@ int __weak kvm_arch_create_vm_debugfs(struct kvm *kvm)
>  	return 0;
>  }
>  
> -static struct kvm *kvm_create_vm(unsigned long type)
> +static struct kvm *kvm_create_vm(unsigned long type, int fd)

I don't love passing in @fd, because actually doing anything but printing the
@fd in a string is doomed to fail.

Rather than pass the raw fd, what about passing in just its name?

---
 virt/kvm/kvm_main.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d94c1d9ecaa9..ac76fc7f2e4d 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -964,7 +964,7 @@ static void kvm_destroy_vm_debugfs(struct kvm *kvm)
 	}
 }

-static int kvm_create_vm_debugfs(struct kvm *kvm, int fd)
+static int kvm_create_vm_debugfs(struct kvm *kvm, const char *fdname)
 {
 	static DEFINE_MUTEX(kvm_debugfs_lock);
 	struct dentry *dent;
@@ -987,7 +987,7 @@ static int kvm_create_vm_debugfs(struct kvm *kvm, int fd)
 	if (!debugfs_initialized())
 		return 0;

-	snprintf(dir_name, sizeof(dir_name), "%d-%d", task_pid_nr(current), fd);
+	snprintf(dir_name, sizeof(dir_name), "%d-%s", task_pid_nr(current), fdname);
 	mutex_lock(&kvm_debugfs_lock);
 	dent = debugfs_lookup(dir_name, kvm_debugfs_dir);
 	if (dent) {
@@ -1076,7 +1076,7 @@ int __weak kvm_arch_create_vm_debugfs(struct kvm *kvm)
 	return 0;
 }

-static struct kvm *kvm_create_vm(unsigned long type, int fd)
+static struct kvm *kvm_create_vm(unsigned long type, const char * fdname)
 {
 	struct kvm *kvm = kvm_arch_alloc_vm();
 	struct kvm_memslots *slots;
@@ -1174,7 +1174,7 @@ static struct kvm *kvm_create_vm(unsigned long type, int fd)
 		goto out_err_mmu_notifier;
 	}

-	r = kvm_create_vm_debugfs(kvm, fd);
+	r = kvm_create_vm_debugfs(kvm, fdname);
 	if (r)
 		goto out_err;

@@ -4781,6 +4781,7 @@ EXPORT_SYMBOL_GPL(file_is_kvm);

 static int kvm_dev_ioctl_create_vm(unsigned long type)
 {
+	char fdname[ITOA_MAX_LEN + 1];
 	int r, fd;
 	struct kvm *kvm;
 	struct file *file;
@@ -4789,7 +4790,9 @@ static int kvm_dev_ioctl_create_vm(unsigned long type)
 	if (fd < 0)
 		return fd;

-	kvm = kvm_create_vm(type, fd);
+	snprintf(fdname, sizeof(fdname), "%d", fd);
+
+	kvm = kvm_create_vm(type, fdname);
 	if (IS_ERR(kvm)) {
 		r = PTR_ERR(kvm);
 		goto put_fd;

base-commit: 3d7c3ff77a78f103c2cf1104157a4132f56fd6d1
--