From mboxrd@z Thu Jan 1 00:00:00 1970 From: Samuel Thibault Subject: [RFC] MM: stub domains and page ownership for mapping in dom0 Date: Thu, 6 Mar 2008 18:52:17 +0000 Message-ID: <20080306185217.GC10848@implementation.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org In the case of an ioemu stubdomain with SDL or vnc server running in dom0, we want to have the stubdomain expose the HVM guest's video RAM through PVFB. However, to map the pages from dom0, xenfb uses xc_map_foreign_pages with the stubdomain ID as domid (since that is what is advertised in the PVFB protocol, and needed for other parts of the protocol), and thus get_page_from_l1e() complains because the stubdomain is not the owner of the pages. In such case, this patch checks that the stubdomain has privileges on the actual owner of the pages, and then accept the mapping. Any red flag? Signed-off-by: Samuel Thibault diff -r fb74347d80c3 xen/arch/x86/mm.c --- a/xen/arch/x86/mm.c Wed Mar 05 12:20:40 2008 +0000 +++ b/xen/arch/x86/mm.c Thu Mar 06 18:35:55 2008 +0000 @@ -673,6 +673,14 @@ get_page_from_l1e return 1; } + /* Let privileged domains transfer the right to map their target domain's + * pages */ + { + struct domain *owner = page_get_owner(page); + if (d != owner && IS_PRIV_FOR(d, owner)) + d = owner; + } + /* Foreign mappings into guests in shadow external mode don't * contribute to writeable mapping refcounts. (This allows the * qemu-dm helper process in dom0 to map the domain's memory without