From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrea Arcangeli Subject: Re: KVM: MMU: large page update_pte issue with non-PAE 32-bit guests Date: Tue, 10 Jun 2008 00:33:49 +0200 Message-ID: <20080609223349.GQ8047@duo.random> References: <20080609023549.GA11092@dmt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Avi Kivity , kvm-devel To: Marcelo Tosatti Return-path: Received: from host36-195-149-62.serverdedicati.aruba.it ([62.149.195.36]:46596 "EHLO mx.cpushare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760657AbYFIWdw (ORCPT ); Mon, 9 Jun 2008 18:33:52 -0400 Content-Disposition: inline In-Reply-To: <20080609023549.GA11092@dmt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: On Sun, Jun 08, 2008 at 11:35:49PM -0300, Marcelo Tosatti wrote: > > kvm_mmu_pte_write() does not handle 32-bit non-PAE large page backed > guests properly. It will instantiate two 2MB sptes pointing to the same > physical 2MB page when a guest large pte update is trapped. > > Instead of duplicating code to handle this, disallow directory level > updates to happen through kvm_mmu_pte_write(), so the two 2MB sptes > emulating one guest 4MB pte can be correctly created by the page fault > handling path. This fix reminded me of this stack trace I looked some time ago, it was also related to a 4M user pte IIRC, may they be related? In such a case we can should update the bug status. http://sourceforge.net/tracker/index.php?func=detail&aid=1929279&group_id=180599&atid=893831 7916:Mar 30 11:18:59 hmf kernel: RIP: 0010:[] [] :kvm:rmap_remove+0x12d/0x1e0 7917:Mar 30 11:18:59 hmf kernel: RSP: 0018:ffff8100715a1a98 EFLAGS: 00010296 7918:Mar 30 11:18:59 hmf kernel: RAX: 0000000000000031 RBX: ffff810001a62f98 RCX: ffffffff80b04168 7919:Mar 30 11:18:59 hmf kernel: RDX: ffffffff80b04168 RSI: 0000000000000006 RDI: ffffffff80b04160 7920:Mar 30 11:18:59 hmf kernel: RBP: ffff810005fb2000 R08: 000000e1aeb7ed38 R09: 0000000000000000 7921:Mar 30 11:18:59 hmf kernel: R10: ffff810002c13b60 R11: 0000000000000001 R12: ffff810039518b30 7922:Mar 30 11:18:59 hmf kernel: R13: ffff81007cc78000 R14: 000000002f7b5063 R15: ffff810039518b30 7923:Mar 30 11:18:59 hmf kernel: FS: 00000000ffdff000(0000) GS:ffffffff80b8f000(0000) knlGS:0000000000000000 7924:Mar 30 11:18:59 hmf kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 7925:Mar 30 11:18:59 hmf kernel: CR2: 00002aaaaaafb000 CR3: 000000007dfc0000 CR4: 00000000000006e0 7926:Mar 30 11:18:59 hmf kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 7927:Mar 30 11:18:59 hmf kernel: DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 7928:Mar 30 11:18:59 hmf kernel: Process qemu-system-x86 (pid: 6262, threadinfo ffff8100715a0000, task ffff81000e90a810) 7929:Mar 30 11:18:59 hmf kernel: Stack: ffff810079af4fa0 0000000000000000 ffff810005fb2000 ffff81000e99c040 7930:Mar 30 11:18:59 hmf kernel: ffff81000e99c040 ffffffff8882e870 00000000040df863 ffffffff8882f3fe 7931:Mar 30 11:18:59 hmf kernel: ffff810000000001 000000000000000f 0000000000000000 00000000c0600000 7932:Mar 30 11:18:59 hmf kernel: Call Trace: 7933:Mar 30 11:18:59 hmf kernel: [] :kvm:kvm_mmu_pte_write+0x220/0x850 7934:Mar 30 11:18:59 hmf kernel: [] :kvm:paging64_walk_addr+0x29e/0x340 7935:Mar 30 11:18:59 hmf kernel: [] :kvm:__emulator_write_phys+0x44/0x70 7936:Mar 30 11:18:59 hmf kernel: [] :kvm:emulator_write_emulated_onepage+0xba/0x150 7937:Mar 30 11:18:59 hmf kernel: [] :kvm:x86_emulate_insn+0x419/0x4430 7938:Mar 30 11:18:59 hmf kernel: [] :kvm_amd:svm_get_segment+0xb/0xa0 7939:Mar 30 11:18:59 hmf kernel: [] :kvm:kvm_get_cs_db_l_bits+0x1e/0x40 7940:Mar 30 11:18:59 hmf kernel: [] :kvm:emulate_instruction+0x1df/0x340 7941:Mar 30 11:18:59 hmf kernel: [] :kvm:kvm_mmu_page_fault+0x58/0x90 Thanks!