From ffb73c140637a39e62aec18d26dcfcbbdfcafb61 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 28 Aug 2017 12:23:22 +0200 Subject: [PATCH] gnttab: avoid spurious maptrack handle allocation failures When no memory is available in the hypervisor, rather than immediately failing the request, try to steal a handle from another vCPU. Reported-by: George Dunlap Signed-off-by: Jan Beulich Reviewed-by: Andrew Cooper master commit: d02f1a0b7576bafb2fba903c7e6e7221ab0d2847 master date: 2017-08-17 14:41:01 +0200 --- xen/common/grant_table.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c index 3e026a3583..5e3678a5f4 100644 --- a/xen/common/grant_table.c +++ b/xen/common/grant_table.c @@ -411,7 +411,7 @@ get_maptrack_handle( struct vcpu *curr = current; unsigned int i, head; grant_handle_t handle; - struct grant_mapping *new_mt; + struct grant_mapping *new_mt = NULL; handle = __get_maptrack_handle(lgt, curr); if ( likely(handle != -1) ) @@ -420,10 +420,15 @@ get_maptrack_handle( spin_lock(&lgt->maptrack_lock); /* - * If we've run out of frames, try stealing an entry from another - * VCPU (in case the guest isn't mapping across its VCPUs evenly). + * If we've run out of handles and still have frame headroom, try + * allocating a new maptrack frame. If there is no headroom, or we're + * out of memory, try stealing an entry from another VCPU (in case the + * guest isn't mapping across its VCPUs evenly). */ - if ( nr_maptrack_frames(lgt) >= max_maptrack_frames ) + if ( nr_maptrack_frames(lgt) < max_maptrack_frames ) + new_mt = alloc_xenheap_page(); + + if ( !new_mt ) { spin_unlock(&lgt->maptrack_lock); @@ -446,12 +451,6 @@ get_maptrack_handle( return steal_maptrack_handle(lgt, curr); } - new_mt = alloc_xenheap_page(); - if ( !new_mt ) - { - spin_unlock(&lgt->maptrack_lock); - return -1; - } clear_page(new_mt); /* -- 2.39.5