KVM: stats: Support binary stats retrieval for a VM

Add a VM ioctl to get a statistics file descriptor by which a read
functionality is provided for userspace to read out VM stats header,
descriptors and data.
Define VM statistics descriptors and header for all architectures.

Reviewed-by: David Matlack <dmatlack@google.com>
Reviewed-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com> #arm64
Signed-off-by: Jing Zhang <jingzhangos@google.com>
Message-Id: <20210618222709.1858088-4-jingzhangos@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index cec986487b30..33ec43a87d0f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4055,6 +4055,42 @@ static int kvm_vm_ioctl_enable_cap_generic(struct kvm *kvm,
 	}
 }
 
+static ssize_t kvm_vm_stats_read(struct file *file, char __user *user_buffer,
+			      size_t size, loff_t *offset)
+{
+	struct kvm *kvm = file->private_data;
+
+	return kvm_stats_read(kvm->stats_id, &kvm_vm_stats_header,
+				&kvm_vm_stats_desc[0], &kvm->stat,
+				sizeof(kvm->stat), user_buffer, size, offset);
+}
+
+static const struct file_operations kvm_vm_stats_fops = {
+	.read = kvm_vm_stats_read,
+	.llseek = noop_llseek,
+};
+
+static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm)
+{
+	int fd;
+	struct file *file;
+
+	fd = get_unused_fd_flags(O_CLOEXEC);
+	if (fd < 0)
+		return fd;
+
+	file = anon_inode_getfile("kvm-vm-stats",
+			&kvm_vm_stats_fops, kvm, O_RDONLY);
+	if (IS_ERR(file)) {
+		put_unused_fd(fd);
+		return PTR_ERR(file);
+	}
+	file->f_mode |= FMODE_PREAD;
+	fd_install(fd, file);
+
+	return fd;
+}
+
 static long kvm_vm_ioctl(struct file *filp,
 			   unsigned int ioctl, unsigned long arg)
 {
@@ -4237,6 +4273,9 @@ static long kvm_vm_ioctl(struct file *filp,
 	case KVM_RESET_DIRTY_RINGS:
 		r = kvm_vm_ioctl_reset_dirty_pages(kvm);
 		break;
+	case KVM_GET_STATS_FD:
+		r = kvm_vm_ioctl_get_stats_fd(kvm);
+		break;
 	default:
 		r = kvm_arch_vm_ioctl(filp, ioctl, arg);
 	}
@@ -4316,6 +4355,9 @@ static int kvm_dev_ioctl_create_vm(unsigned long type)
 	if (r < 0)
 		goto put_kvm;
 
+	snprintf(kvm->stats_id, sizeof(kvm->stats_id),
+			"kvm-%d", task_pid_nr(current));
+
 	file = anon_inode_getfile("kvm-vm", &kvm_vm_fops, kvm, O_RDWR);
 	if (IS_ERR(file)) {
 		put_unused_fd(r);