From 1ab3eea9d8873cb0c60e59d55a89c2f1842a5063 Mon Sep 17 00:00:00 2001 From: Tim Deegan Date: Thu, 7 Mar 2013 14:08:24 +0000 Subject: [PATCH] x86/mem_sharing: check for errors in p2m->set_entry(). This call ought always to succeed. Assert that it does rather than ignoring the return value. Signed-off-by: Tim Deegan Acked-by: Andres Lagar-Cavilla Acked-by: Jan Beulich --- xen/arch/x86/mm/mem_sharing.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c index 1caa9000fc..0364bb048e 100644 --- a/xen/arch/x86/mm/mem_sharing.c +++ b/xen/arch/x86/mm/mem_sharing.c @@ -1273,6 +1273,8 @@ int relinquish_shared_pages(struct domain *d) p2m_access_t a; p2m_type_t t; mfn_t mfn; + int set_rc; + if ( atomic_read(&d->shr_pages) == 0 ) break; mfn = p2m->get_entry(p2m, gfn, &t, &a, 0, NULL); @@ -1281,10 +1283,12 @@ int relinquish_shared_pages(struct domain *d) /* Does not fail with ENOMEM given the DESTROY flag */ BUG_ON(__mem_sharing_unshare_page(d, gfn, MEM_SHARING_DESTROY_GFN)); - /* Clear out the p2m entry so no one else may try to - * unshare */ - p2m->set_entry(p2m, gfn, _mfn(0), PAGE_ORDER_4K, - p2m_invalid, p2m_access_rwx); + /* Clear out the p2m entry so no one else may try to + * unshare. Must succeed: we just read the old entry and + * we hold the p2m lock. */ + set_rc = p2m->set_entry(p2m, gfn, _mfn(0), PAGE_ORDER_4K, + p2m_invalid, p2m_access_rwx); + ASSERT(set_rc != 0); count++; } -- 2.39.5