From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: [PATCH] Make pte writes in map_pages_to_xen() atomic Date: Sun, 15 Apr 2007 18:53:07 +0300 Message-ID: <46224A63.2000408@qumranet.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------050305080108000807000309" Cc: kvm-devel , Jeremy Fitzhardinge To: xen-devel Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org This is a multi-part message in MIME format. --------------050305080108000807000309 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit With debug=y, Xen calls map_pages_to_xen() to remap its own page tables. On pae builds, the pte writes are nonatomic. This causes Xen to crash under kvm (and presumably under other shadow page table caching VMMs), because after the first half of the pte update, the code under eip is no longer accessible. It's also possible under bare metal if an SMI arrives exactly at the wrong moment, and in addition that SMI flushes the tlb. Fix by using atomic pte writes. With this, xen pae debug=y boots under kvm. Reported by Jeremy Fitzhardinge . Signed-off-by: Avi Kivity -- error compiling committee.c: too many arguments to function --------------050305080108000807000309 Content-Type: text/x-patch; name="make-map_pages_to_xen-atomic.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="make-map_pages_to_xen-atomic.patch" diff -r 039daabebad5 xen/arch/x86/mm.c --- a/xen/arch/x86/mm.c Fri Apr 13 16:07:48 2007 +0100 +++ b/xen/arch/x86/mm.c Sun Apr 15 18:36:59 2007 +0300 @@ -3454,14 +3454,14 @@ int map_pages_to_xen( l1e_write(&pl1e[i], l1e_from_pfn(l2e_get_pfn(*pl2e) + i, l2e_get_flags(*pl2e) & ~_PAGE_PSE)); - l2e_write(pl2e, l2e_from_pfn(virt_to_mfn(pl1e), + l2e_write_atomic(pl2e, l2e_from_pfn(virt_to_mfn(pl1e), __PAGE_HYPERVISOR)); local_flush_tlb_pge(); } pl1e = l2e_to_l1e(*pl2e) + l1_table_offset(virt); ol1e = *pl1e; - l1e_write(pl1e, l1e_from_pfn(mfn, flags)); + l1e_write_atomic(pl1e, l1e_from_pfn(mfn, flags)); if ( (l1e_get_flags(ol1e) & _PAGE_PRESENT) ) local_flush_tlb_one(virt); --------------050305080108000807000309 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ --------------050305080108000807000309 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ kvm-devel mailing list kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org https://lists.sourceforge.net/lists/listinfo/kvm-devel --------------050305080108000807000309--