[Xen-devel] [PATCH RFC 44/49] xen: round up max vcpus to scheduling granularity

[Juergen Gross <jgross@xxxxxxxx>]

Make sure the number of vcpus is always a multiple of the scheduling
granularity. Note that we don't support a scheduling granularity above
one on ARM.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/dom0_build.c | 1 +
 xen/common/domain.c       | 1 +
 xen/common/domctl.c       | 1 +
 xen/include/xen/sched.h   | 5 +++++
 4 files changed, 8 insertions(+)

diff --git a/xen/arch/x86/dom0_build.c b/xen/arch/x86/dom0_build.c
index 77b5646424..76a81dd4a9 100644
--- a/xen/arch/x86/dom0_build.c
+++ b/xen/arch/x86/dom0_build.c
@@ -258,6 +258,7 @@ unsigned int __init dom0_max_vcpus(void)
         max_vcpus = opt_dom0_max_vcpus_min;
     if ( opt_dom0_max_vcpus_max < max_vcpus )
         max_vcpus = opt_dom0_max_vcpus_max;
+    max_vcpus = sched_max_vcpus(max_vcpus);
     limit = dom0_pvh ? HVM_MAX_VCPUS : MAX_VIRT_CPUS;
     if ( max_vcpus > limit )
         max_vcpus = limit;
diff --git a/xen/common/domain.c b/xen/common/domain.c
index b448d20d40..d338a2204c 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -290,6 +290,7 @@ static int sanitise_domain_config(struct 
xen_domctl_createdomain *config)
         return -EINVAL;
     }
 
+    config->max_vcpus = sched_max_vcpus(config->max_vcpus);
     if ( config->max_vcpus < 1 )
     {
         dprintk(XENLOG_INFO, "No vCPUS\n");
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index ccde1ba706..80837a2a5e 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -542,6 +542,7 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
     {
         unsigned int i, max = op->u.max_vcpus.max;
 
+        max = sched_max_vcpus(max);
         ret = -EINVAL;
         if ( (d == current->domain) || /* no domain_pause() */
              (max != d->max_vcpus) )   /* max_vcpus set up in createdomain */
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 52a1abfca9..314a453a60 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -490,6 +490,11 @@ extern struct vcpu *idle_vcpu[NR_CPUS];
 
 extern unsigned int sched_granularity;
 
+static inline unsigned int sched_max_vcpus(unsigned int n_vcpus)
+{
+    return DIV_ROUND_UP(n_vcpus, sched_granularity) * sched_granularity;
+}
+
 static inline bool is_system_domain(const struct domain *d)
 {
     return d->domain_id >= DOMID_FIRST_RESERVED;
-- 
2.16.4


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