[PATCH v4 3/5] xen/cpupool: add cpupool directories

[Juergen Gross <jgross@xxxxxxxx>]

Add /cpupool/<cpupool-id> directories to hypfs. Those are completely
dynamic, so the related hypfs access functions need to be implemented.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx>
---
V2:
- added const (Jan Beulich)
- call hypfs_add_dir() in helper (Dario Faggioli)
- switch locking to enter/exit callbacks

V3:
- use generic dyndirid enter function
- const for hypfs function vector (Jan Beulich)
- drop size calculation from cpupool_dir_read() (Jan Beulich)
- check cpupool id to not exceed UINT_MAX (Jan Beulich)
- coding style (#if/#else/#endif) (Jan Beulich)
---
 docs/misc/hypfs-paths.pandoc |   9 +++
 xen/common/sched/cpupool.c   | 104 +++++++++++++++++++++++++++++++++++
 2 files changed, 113 insertions(+)

diff --git a/docs/misc/hypfs-paths.pandoc b/docs/misc/hypfs-paths.pandoc
index 6c7b2f7ee3..aaca1cdf92 100644
--- a/docs/misc/hypfs-paths.pandoc
+++ b/docs/misc/hypfs-paths.pandoc
@@ -175,6 +175,15 @@ The major version of Xen.
 
 The minor version of Xen.
 
+#### /cpupool/
+
+A directory of all current cpupools.
+
+#### /cpupool/*/
+
+The individual cpupools. Each entry is a directory with the name being the
+cpupool-id (e.g. /cpupool/0/).
+
 #### /params/
 
 A directory of runtime parameters.
diff --git a/xen/common/sched/cpupool.c b/xen/common/sched/cpupool.c
index 0db7d77219..f293ba0cc4 100644
--- a/xen/common/sched/cpupool.c
+++ b/xen/common/sched/cpupool.c
@@ -13,6 +13,8 @@
 
 #include <xen/cpu.h>
 #include <xen/cpumask.h>
+#include <xen/guest_access.h>
+#include <xen/hypfs.h>
 #include <xen/init.h>
 #include <xen/keyhandler.h>
 #include <xen/lib.h>
@@ -33,6 +35,7 @@ static int cpupool_moving_cpu = -1;
 static struct cpupool *cpupool_cpu_moving = NULL;
 static cpumask_t cpupool_locked_cpus;
 
+/* This lock nests inside sysctl or hypfs lock. */
 static DEFINE_SPINLOCK(cpupool_lock);
 
 static enum sched_gran __read_mostly opt_sched_granularity = SCHED_GRAN_cpu;
@@ -1003,12 +1006,113 @@ static struct notifier_block cpu_nfb = {
     .notifier_call = cpu_callback
 };
 
+#ifdef CONFIG_HYPFS
+
+static HYPFS_DIR_INIT(cpupool_pooldir, "%u");
+
+static int cpupool_dir_read(const struct hypfs_entry *entry,
+                            XEN_GUEST_HANDLE_PARAM(void) uaddr)
+{
+    int ret = 0;
+    const struct cpupool *c;
+
+    list_for_each_entry(c, &cpupool_list, list)
+    {
+        ret = hypfs_read_dyndir_id_entry(&cpupool_pooldir, c->cpupool_id,
+                                         list_is_last(&c->list, &cpupool_list),
+                                         &uaddr);
+        if ( ret )
+            break;
+    }
+
+    return ret;
+}
+
+static unsigned int cpupool_dir_getsize(const struct hypfs_entry *entry)
+{
+    const struct cpupool *c;
+    unsigned int size = 0;
+
+    list_for_each_entry(c, &cpupool_list, list)
+        size += hypfs_dynid_entry_size(entry, c->cpupool_id);
+
+    return size;
+}
+
+static const struct hypfs_entry *cpupool_dir_enter(
+    const struct hypfs_entry *entry)
+{
+    struct hypfs_dyndir_id *data;
+
+    data = hypfs_alloc_dyndata(struct hypfs_dyndir_id);
+    if ( !data )
+        return ERR_PTR(-ENOMEM);
+    data->id = CPUPOOLID_NONE;
+
+    spin_lock(&cpupool_lock);
+
+    return entry;
+}
+
+static void cpupool_dir_exit(const struct hypfs_entry *entry)
+{
+    spin_unlock(&cpupool_lock);
+
+    hypfs_free_dyndata();
+}
+
+static struct hypfs_entry *cpupool_dir_findentry(
+    const struct hypfs_entry_dir *dir, const char *name, unsigned int name_len)
+{
+    unsigned long id;
+    const char *end;
+    struct cpupool *cpupool;
+
+    id = simple_strtoul(name, &end, 10);
+    if ( end != name + name_len || id > UINT_MAX )
+        return ERR_PTR(-ENOENT);
+
+    cpupool = __cpupool_find_by_id(id, true);
+
+    if ( !cpupool )
+        return ERR_PTR(-ENOENT);
+
+    return hypfs_gen_dyndir_id_entry(&cpupool_pooldir, id, cpupool);
+}
+
+static const struct hypfs_funcs cpupool_dir_funcs = {
+    .enter = cpupool_dir_enter,
+    .exit = cpupool_dir_exit,
+    .read = cpupool_dir_read,
+    .write = hypfs_write_deny,
+    .getsize = cpupool_dir_getsize,
+    .findentry = cpupool_dir_findentry,
+};
+
+static HYPFS_DIR_INIT_FUNC(cpupool_dir, "cpupool", &cpupool_dir_funcs);
+
+static void cpupool_hypfs_init(void)
+{
+    hypfs_add_dir(&hypfs_root, &cpupool_dir, true);
+    hypfs_add_dyndir(&cpupool_dir, &cpupool_pooldir);
+}
+
+#else /* CONFIG_HYPFS */
+
+static void cpupool_hypfs_init(void)
+{
+}
+
+#endif /* CONFIG_HYPFS */
+
 static int __init cpupool_init(void)
 {
     unsigned int cpu;
 
     cpupool_gran_init();
 
+    cpupool_hypfs_init();
+
     cpupool0 = cpupool_create(0, 0);
     BUG_ON(IS_ERR(cpupool0));
     cpupool_put(cpupool0);
-- 
2.26.2