From 2eba88c6af6c2649ce768d5bbb8732ce6f1b8d52 Mon Sep 17 00:00:00 2001 From: Keir Fraser Date: Thu, 12 Nov 2009 11:39:51 +0000 Subject: [PATCH] PoD: Handle operations properly when domain is dying No populate-on-demand activities should happen when a domain is dying. Especially, it is a bug for memory to be added to the PoD cache when d->is_dying is non-zero, since if this happens after the cache has been emptied, these pages will never be freed. This may cause "zombie domains" to linger. Signed-off-by: George Dunlap --- xen/arch/x86/mm/p2m.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c index 66069ce442..aebfdd18a6 100644 --- a/xen/arch/x86/mm/p2m.c +++ b/xen/arch/x86/mm/p2m.c @@ -303,6 +303,8 @@ p2m_pod_cache_add(struct domain *d, BUG(); } + BUG_ON(d->is_dying); + spin_unlock(&d->page_alloc_lock); return 0; @@ -503,6 +505,10 @@ p2m_pod_set_mem_target(struct domain *d, unsigned long target) if ( p2md->pod.entry_count == 0 ) goto out; + /* Don't do anything if the domain is being torn down */ + if ( d->is_dying ) + goto out; + /* T' < B: Don't reduce the cache size; let the balloon driver * take care of it. */ if ( target < d->tot_pages ) @@ -582,7 +588,7 @@ p2m_pod_decrease_reservation(struct domain *d, /* If we don't have any outstanding PoD entries, let things take their * course */ - if ( p2md->pod.entry_count == 0 ) + if ( p2md->pod.entry_count == 0 || unlikely(d->is_dying) ) goto out; /* Figure out if we need to steal some freed memory for our cache */ @@ -1002,6 +1008,12 @@ p2m_pod_demand_populate(struct domain *d, unsigned long gfn, struct p2m_domain *p2md = d->arch.p2m; int i; + /* This check is done with the p2m lock held. This will make sure that + * even if d->is_dying changes under our feet, empty_pod_cache() won't start + * until we're done. */ + if ( unlikely(d->is_dying) ) + goto out_fail; + /* If we're low, start a sweep */ if ( order == 9 && page_list_empty(&p2md->pod.super) ) p2m_pod_emergency_sweep_super(d); @@ -1048,6 +1060,7 @@ out_of_memory: printk("%s: Out of populate-on-demand memory! tot_pages %" PRIu32 " pod_entries %" PRIi32 "\n", __func__, d->tot_pages, p2md->pod.entry_count); domain_crash(d); +out_fail: return -1; remap_and_retry: BUG_ON(order != 9); -- 2.30.2