From: Nai Xia Date: Tue, 6 Aug 2013 16:25:48 +0000 (+0800) Subject: mem_sharing_nominate_page: p2mt should never change before p2m_change_type() X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~6544^2 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=fa89d08f329e495f20a561a0dac80c325c8b7784;p=xen.git mem_sharing_nominate_page: p2mt should never change before p2m_change_type() The p2mt change check for p2m_change_type() was first introduced when this code path was not protected by p2m_lock(). Now this code path is protected by p2m_lock. So p2mt should never change before p2m_change_type(). Signed-off-by: Nai Xia Acked-by: Andres Lagar-Cavilla Acked-by: Tim Deegan --- diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c index 0364bb048e..1e89f6c4fc 100644 --- a/xen/arch/x86/mm/mem_sharing.c +++ b/xen/arch/x86/mm/mem_sharing.c @@ -900,20 +900,8 @@ int mem_sharing_nominate_page(struct domain *d, goto out; } - /* Change the p2m type */ - if ( p2m_change_type(d, gfn, p2mt, p2m_ram_shared) != p2mt ) - { - /* This is unlikely, as the type must have changed since we've checked - * it a few lines above. - * The mfn needs to revert back to rw type. This should never fail, - * since no-one knew that the mfn was temporarily sharable */ - mem_sharing_gfn_destroy(page, d, gfn_info); - xfree(page->sharing); - page->sharing = NULL; - /* NOTE: We haven't yet added this to the audit list. */ - BUG_ON(page_make_private(d, page) != 0); - goto out; - } + /* Change the p2m type, should never fail with p2m locked. */ + BUG_ON(p2m_change_type(d, gfn, p2mt, p2m_ram_shared) != p2mt); /* Account for this page. */ atomic_inc(&nr_shared_mfns);