s390/hypfs: factor out filesystem code

The s390_hypfs filesystem is deprecated and shouldn't be used due to its
rather odd semantics. It creates a whole directory structure with static
file contents so a user can read a consistent state while within that
directory.
Writing to its update attribute will remove and rebuild nearly the whole
filesystem, so that again a user can read a consistent state, even if
multiple files need to be read.

Given that this wastes a lot of CPU cycles, and involves a lot of code,
binary interfaces have been added quite a couple of years ago, which simply
pass the binary data to user space, and let user space decode the data.
This is the preferred and only way how the data should be retrieved.

The assumption is that there are no users of the s390_hypfs filesystem.
However instead of just removing the code, and having to revert in case
there are actually users, factor the filesystem code out and make it only
available via a new config option.

This config option is supposed to be disabled. If it turns out there are no
complaints the filesystem code can be removed probably in a couple of
years.

Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

1 files changed, 50 insertions, 0 deletions

diff --git a/arch/s390/hypfs/hypfs_vm.h b/arch/s390/hypfs/hypfs_vm.h
new file mode 100644
index 000000000000..fe2e5851addd
--- /dev/null
+++ b/arch/s390/hypfs/hypfs_vm.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *    Hypervisor filesystem for Linux on s390. z/VM implementation.
+ *
+ *    Copyright IBM Corp. 2006
+ *    Author(s): Michael Holzheu <holzheu@de.ibm.com>
+ */
+
+#ifndef _S390_HYPFS_VM_H_
+#define _S390_HYPFS_VM_H_
+
+#define DIAG2FC_NAME_LEN 8
+
+struct diag2fc_data {
+	__u32 version;
+	__u32 flags;
+	__u64 used_cpu;
+	__u64 el_time;
+	__u64 mem_min_kb;
+	__u64 mem_max_kb;
+	__u64 mem_share_kb;
+	__u64 mem_used_kb;
+	__u32 pcpus;
+	__u32 lcpus;
+	__u32 vcpus;
+	__u32 ocpus;
+	__u32 cpu_max;
+	__u32 cpu_shares;
+	__u32 cpu_use_samp;
+	__u32 cpu_delay_samp;
+	__u32 page_wait_samp;
+	__u32 idle_samp;
+	__u32 other_samp;
+	__u32 total_samp;
+	char  guest_name[DIAG2FC_NAME_LEN];
+};
+
+struct diag2fc_parm_list {
+	char userid[DIAG2FC_NAME_LEN];
+	char aci_grp[DIAG2FC_NAME_LEN];
+	__u64 addr;
+	__u32 size;
+	__u32 fmt;
+};
+
+void *diag2fc_store(char *query, unsigned int *count, int offset);
+void diag2fc_free(const void *data);
+extern char *diag2fc_guest_query;
+
+#endif /* _S390_HYPFS_VM_H_ */