[xen staging] xen/cpupool: Allow cpupool0 to use different scheduler

[patchbot@xxxxxxx]

commit 0badfb110fa33ca9ffd3bdc3a5200cded03e6106
Author:     Luca Fancellu <luca.fancellu@xxxxxxx>
AuthorDate: Fri May 6 13:00:12 2022 +0100
Commit:     Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
CommitDate: Mon May 9 13:33:03 2022 -0700

    xen/cpupool: Allow cpupool0 to use different scheduler
    
    Currently cpupool0 can use only the default scheduler, and
    cpupool_create has an hardcoded behavior when creating the pool 0
    that doesn't allocate new memory for the scheduler, but uses the
    default scheduler structure in memory.
    
    With this commit it is possible to allocate a different scheduler for
    the cpupool0 when using the boot time cpupool.
    To achieve this the hardcoded behavior in cpupool_create is removed
    and the cpupool0 creation is moved.
    
    When compiling without boot time cpupools enabled, the current
    behavior is maintained (except that cpupool0 scheduler memory will be
    allocated).
    
    Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
    Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/common/sched/boot-cpupool.c | 5 ++++-
 xen/common/sched/cpupool.c      | 8 +-------
 xen/include/xen/sched.h         | 5 ++++-
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/xen/common/sched/boot-cpupool.c b/xen/common/sched/boot-cpupool.c
index 240bae4ceb..5955e6f9a9 100644
--- a/xen/common/sched/boot-cpupool.c
+++ b/xen/common/sched/boot-cpupool.c
@@ -205,8 +205,11 @@ void __init btcpupools_allocate_pools(void)
     if ( add_extra_cpupool )
         next_pool_id++;
 
+    /* Keep track of cpupool id 0 with the global cpupool0 */
+    cpupool0 = cpupool_create_pool(0, pool_sched_map[0]);
+
     /* Create cpupools with selected schedulers */
-    for ( i = 0; i < next_pool_id; i++ )
+    for ( i = 1; i < next_pool_id; i++ )
         cpupool_create_pool(i, pool_sched_map[i]);
 }
 
diff --git a/xen/common/sched/cpupool.c b/xen/common/sched/cpupool.c
index 0a93bcc631..f6e3d97e52 100644
--- a/xen/common/sched/cpupool.c
+++ b/xen/common/sched/cpupool.c
@@ -312,10 +312,7 @@ static struct cpupool *cpupool_create(unsigned int poolid,
         c->cpupool_id = q->cpupool_id + 1;
     }
 
-    if ( poolid == 0 )
-        c->sched = scheduler_get_default();
-    else
-        c->sched = scheduler_alloc(sched_id);
+    c->sched = scheduler_alloc(sched_id);
     if ( IS_ERR(c->sched) )
     {
         ret = PTR_ERR(c->sched);
@@ -1248,9 +1245,6 @@ static int __init cf_check cpupool_init(void)
 
     cpupool_hypfs_init();
 
-    cpupool0 = cpupool_create(0, 0);
-    BUG_ON(IS_ERR(cpupool0));
-    cpupool_put(cpupool0);
     register_cpu_notifier(&cpu_nfb);
 
     btcpupools_dtb_parse();
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 653317cf4d..463d41ffb6 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -1196,7 +1196,10 @@ void btcpupools_dtb_parse(void);
 int btcpupools_get_domain_pool_id(const struct dt_device_node *node);
 
 #else /* !CONFIG_BOOT_TIME_CPUPOOLS */
-static inline void btcpupools_allocate_pools(void) {}
+static inline void btcpupools_allocate_pools(void)
+{
+    cpupool0 = cpupool_create_pool(0, -1);
+}
 static inline void btcpupools_dtb_parse(void) {}
 static inline unsigned int btcpupools_get_cpupool_id(unsigned int cpu)
 {
--
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