[xen staging] xen/cpupool: limit number of cpupools

[patchbot@xxxxxxx]

commit 488a15a669e5b83267590ed8dad2428a5216ee87
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Fri May 20 12:19:06 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri May 20 12:19:06 2022 +0200

    xen/cpupool: limit number of cpupools
    
    Today the number of cpupools in a system is unlimited. This can lead to
    multiple problems (e.g. duplicate cpupool-id or scalability issues).
    
    Limit the number of cpupools to twice the number of maximum possible
    cpus, allowing to have one cpupool per physical cpu plus some spare
    cpupools for special means (there are already existing use cases for
    such spare cpupools).
    
    Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/common/sched/cpupool.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/xen/common/sched/cpupool.c b/xen/common/sched/cpupool.c
index f1aa2db5f4..a20e3a5fcb 100644
--- a/xen/common/sched/cpupool.c
+++ b/xen/common/sched/cpupool.c
@@ -30,6 +30,7 @@ struct cpupool *cpupool0;                /* Initial cpupool 
with Dom0 */
 cpumask_t cpupool_free_cpus;             /* cpus not in any cpupool */
 
 static LIST_HEAD(cpupool_list);          /* linked list, sorted by poolid */
+static unsigned int n_cpupools;
 
 static int cpupool_moving_cpu = -1;
 static struct cpupool *cpupool_cpu_moving = NULL;
@@ -276,6 +277,14 @@ static struct cpupool *cpupool_create(unsigned int poolid,
 
     spin_lock(&cpupool_lock);
 
+    /* Don't allow too many cpupools. */
+    if ( n_cpupools >= 2 * nr_cpu_ids )
+    {
+        ret = -ENOSPC;
+        goto unlock;
+    }
+    n_cpupools++;
+
     if ( poolid != CPUPOOLID_NONE )
     {
         q = __cpupool_find_by_id(poolid, false);
@@ -332,7 +341,9 @@ static struct cpupool *cpupool_create(unsigned int poolid,
 
  err:
     list_del(&c->list);
+    n_cpupools--;
 
+ unlock:
     spin_unlock(&cpupool_lock);
 
     free_cpupool_struct(c);
@@ -356,6 +367,7 @@ static int cpupool_destroy(struct cpupool *c)
         return -EBUSY;
     }
 
+    n_cpupools--;
     list_del(&c->list);
 
     spin_unlock(&cpupool_lock);
--
generated by git-patchbot for /home/xen/git/xen.git#staging