[PATCH for-4.5] xen/common: Process softirqs while dumping domains

[PATCH for-4.5] xen/common: Process softirqs while dumping domains

[Andrew Cooper]

Process softirqs once per domain, and once every 64 vcpus in a guest to avoid
being hit by the NMI watchdog.  Discovered against a VM which had accidentally
been assigned 8192 vcpus.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <JBeulich@suse.com>
CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 xen/common/keyhandler.c |    9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/xen/common/keyhandler.c b/xen/common/keyhandler.c
index 809378c..c9d9206 100644
--- a/xen/common/keyhandler.c
+++ b/xen/common/keyhandler.c
@@ -253,6 +253,9 @@ static void dump_domains(unsigned char key)
     for_each_domain ( d )
     {
         unsigned int i;
+
+        process_pending_softirqs();
+
         printk("General information for domain %u:\n", d->domain_id);
         cpuset_print(tmpstr, sizeof(tmpstr), d->domain_dirty_cpumask);
         printk("    refcnt=%d dying=%d pause_count=%d\n",
@@ -287,6 +290,9 @@ static void dump_domains(unsigned char key)
                d->domain_id);
         for_each_vcpu ( d, v )
         {
+            if ( (v->vcpu_id & 0x3f) == 0 )
+                process_pending_softirqs();
+
             printk("    VCPU%d: CPU%d [has=%c] poll=%d "
                    "upcall_pend = %02x, upcall_mask = %02x ",
                    v->vcpu_id, v->processor,
@@ -311,6 +317,9 @@ static void dump_domains(unsigned char key)
     {
         for_each_vcpu ( d, v )
         {
+            if ( (v->vcpu_id & 0x3f) == 0 )
+                process_pending_softirqs();
+
             printk("Notifying guest %d:%d (virq %d, port %d)\n",
                    d->domain_id, v->vcpu_id,
                    VIRQ_DEBUG, v->virq_to_evtchn[VIRQ_DEBUG]);
-- 
1.7.10.4

Re: [PATCH for-4.5] xen/common: Process softirqs while dumping domains

[Dario Faggioli]

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On Wed, 2014-10-29 at 15:08 +0000, Andrew Cooper wrote:
> Process softirqs once per domain, and once every 64 vcpus in a guest to avoid
> being hit by the NMI watchdog.  Discovered against a VM which had accidentally
> been assigned 8192 vcpus.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>
Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com>

Personally...

> diff --git a/xen/common/keyhandler.c b/xen/common/keyhandler.c
> index 809378c..c9d9206 100644
> --- a/xen/common/keyhandler.c
> +++ b/xen/common/keyhandler.c

> @@ -287,6 +290,9 @@ static void dump_domains(unsigned char key)
>                 d->domain_id);
>          for_each_vcpu ( d, v )
>          {
> +            if ( (v->vcpu_id & 0x3f) == 0 )
> +                process_pending_softirqs();
> +
>
... I think something like ( vcpu_id % 64 ) would have been more
readable, but I understand that's only a matter of taste. :-)

Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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