From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,URIBL_DBL_ABUSE_MALW, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27DD3C3F68F for ; Wed, 5 Feb 2020 23:55:42 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EE66D218AC for ; Wed, 5 Feb 2020 23:55:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="rw1DxA5i" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EE66D218AC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=putX55EX3iOX2kdzsNj0r6uldiCR1UbB5G1AmgDNRNQ=; b=rw1DxA5idIhFpp DvPkd1d+0un1CK7/dlaa2zFBa9aQB2b0vhWF1+K/BBTH3t/BvI88TNOrTJaS9fpctYi9hjriwBs+S zLfHdhZPoEBqrsNQ8zXq6LyrY1ju6kDj6Y4voAH/JcxdcRoJxU7yT55IiWOBBxm/NeYOb28sE/DgP 2l9DtB83oqYwXHWRpk/CNZSZ+se6mcd1rAbXmaXqAqR1VANll4U6NFC2EP7/GmgTfy0YjXPKzE0WG JsB+KJ85CeZIY1b7HKlPbfDvzYhly4yCEbqob2XINaBEN53TZDjAuaUEW7VZsZo5hJAdQNEha3EK2 fc8q7sAUnyIxkuPH18vA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1izUWB-00039I-RK; Wed, 05 Feb 2020 23:55:39 +0000 Received: from mga14.intel.com ([192.55.52.115]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1izUW8-00038h-Sa for linux-arm-kernel@lists.infradead.org; Wed, 05 Feb 2020 23:55:38 +0000 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Feb 2020 15:55:34 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,407,1574150400"; d="scan'208";a="225108744" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.202]) by fmsmga007.fm.intel.com with ESMTP; 05 Feb 2020 15:55:33 -0800 Date: Wed, 5 Feb 2020 15:55:33 -0800 From: Sean Christopherson To: Peter Xu Subject: Re: [PATCH v5 01/19] KVM: x86: Allocate new rmap and large page tracking when moving memslot Message-ID: <20200205235533.GA7631@linux.intel.com> References: <20200121223157.15263-1-sean.j.christopherson@intel.com> <20200121223157.15263-2-sean.j.christopherson@intel.com> <20200205214952.GD387680@xz-x1> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200205214952.GD387680@xz-x1> User-Agent: Mutt/1.5.24 (2015-08-30) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200205_155536_936285_702D374A X-CRM114-Status: GOOD ( 28.47 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Wanpeng Li , kvm@vger.kernel.org, David Hildenbrand , linux-mips@vger.kernel.org, Paul Mackerras , kvmarm@lists.cs.columbia.edu, Janosch Frank , Marc Zyngier , Joerg Roedel , Christian Borntraeger , Julien Thierry , Suzuki K Poulose , kvm-ppc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Jim Mattson , Cornelia Huck , Christoffer Dall , linux-kernel@vger.kernel.org, James Morse , Paolo Bonzini , Vitaly Kuznetsov , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Feb 05, 2020 at 04:49:52PM -0500, Peter Xu wrote: > On Tue, Jan 21, 2020 at 02:31:39PM -0800, Sean Christopherson wrote: > > Reallocate a rmap array and recalcuate large page compatibility when > > moving an existing memslot to correctly handle the alignment properties > > of the new memslot. The number of rmap entries required at each level > > is dependent on the alignment of the memslot's base gfn with respect to > > that level, e.g. moving a large-page aligned memslot so that it becomes > > unaligned will increase the number of rmap entries needed at the now > > unaligned level. > > > > Not updating the rmap array is the most obvious bug, as KVM accesses > > garbage data beyond the end of the rmap. KVM interprets the bad data as > > pointers, leading to non-canonical #GPs, unexpected #PFs, etc... > > > > general protection fault: 0000 [#1] SMP > > CPU: 0 PID: 1909 Comm: move_memory_reg Not tainted 5.4.0-rc7+ #139 > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 > > RIP: 0010:rmap_get_first+0x37/0x50 [kvm] > > Code: <48> 8b 3b 48 85 ff 74 ec e8 6c f4 ff ff 85 c0 74 e3 48 89 d8 5b c3 > > RSP: 0018:ffffc9000021bbc8 EFLAGS: 00010246 > > RAX: ffff00617461642e RBX: ffff00617461642e RCX: 0000000000000012 > > RDX: ffff88827400f568 RSI: ffffc9000021bbe0 RDI: ffff88827400f570 > > RBP: 0010000000000000 R08: ffffc9000021bd00 R09: ffffc9000021bda8 > > R10: ffffc9000021bc48 R11: 0000000000000000 R12: 0030000000000000 > > R13: 0000000000000000 R14: ffff88827427d700 R15: ffffc9000021bce8 > > FS: 00007f7eda014700(0000) GS:ffff888277a00000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 00007f7ed9216ff8 CR3: 0000000274391003 CR4: 0000000000162eb0 > > Call Trace: > > kvm_mmu_slot_set_dirty+0xa1/0x150 [kvm] > > __kvm_set_memory_region.part.64+0x559/0x960 [kvm] > > kvm_set_memory_region+0x45/0x60 [kvm] > > kvm_vm_ioctl+0x30f/0x920 [kvm] > > do_vfs_ioctl+0xa1/0x620 > > ksys_ioctl+0x66/0x70 > > __x64_sys_ioctl+0x16/0x20 > > do_syscall_64+0x4c/0x170 > > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > RIP: 0033:0x7f7ed9911f47 > > Code: <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 21 6f 2c 00 f7 d8 64 89 01 48 > > RSP: 002b:00007ffc00937498 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > > RAX: ffffffffffffffda RBX: 0000000001ab0010 RCX: 00007f7ed9911f47 > > RDX: 0000000001ab1350 RSI: 000000004020ae46 RDI: 0000000000000004 > > RBP: 000000000000000a R08: 0000000000000000 R09: 00007f7ed9214700 > > R10: 00007f7ed92149d0 R11: 0000000000000246 R12: 00000000bffff000 > > R13: 0000000000000003 R14: 00007f7ed9215000 R15: 0000000000000000 > > Modules linked in: kvm_intel kvm irqbypass > > ---[ end trace 0c5f570b3358ca89 ]--- > > > > The disallow_lpage tracking is more subtle. Failure to update results > > in KVM creating large pages when it shouldn't, either due to stale data > > or again due to indexing beyond the end of the metadata arrays, which > > can lead to memory corruption and/or leaking data to guest/userspace. > > > > Note, the arrays for the old memslot are freed by the unconditional call > > to kvm_free_memslot() in __kvm_set_memory_region(). > > If __kvm_set_memory_region() failed, I think the old memslot will be > kept and the new memslot will be freed instead? This is referring to a successful MOVE operation to note that zeroing @arch in kvm_arch_create_memslot() won't leak memory. > > > > Fixes: 05da45583de9b ("KVM: MMU: large page support") > > Cc: stable@vger.kernel.org > > Signed-off-by: Sean Christopherson > > --- > > arch/x86/kvm/x86.c | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index 4c30ebe74e5d..1953c71c52f2 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -9793,6 +9793,13 @@ int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot, > > { > > int i; > > > > + /* > > + * Clear out the previous array pointers for the KVM_MR_MOVE case. The > > + * old arrays will be freed by __kvm_set_memory_region() if installing > > + * the new memslot is successful. > > + */ > > + memset(&slot->arch, 0, sizeof(slot->arch)); > > I actually gave r-b on this patch but it was lost... And then when I > read it again I start to confuse on why we need to set these to zeros. > Even if they're not zeros, iiuc kvm_free_memslot() will compare each > of the array pointer and it will only free the changed pointers, then > it looks fine even without zeroing? It's for the failure path, the out_free label, which blindy calls kvfree() and relies on un-allocated pointers being NULL. If @arch isn't zeroed, the failure path will free metadata from the previous memslot. > > + > > for (i = 0; i < KVM_NR_PAGE_SIZES; ++i) { > > struct kvm_lpage_info *linfo; > > unsigned long ugfn; > > @@ -9867,6 +9874,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, > > const struct kvm_userspace_memory_region *mem, > > enum kvm_mr_change change) > > { > > + if (change == KVM_MR_MOVE) > > + return kvm_arch_create_memslot(kvm, memslot, > > + mem->memory_size >> PAGE_SHIFT); > > + > > Instead of calling kvm_arch_create_memslot() explicitly again here, > can it be replaced by below? > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 72b45f491692..85a7b02fd752 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1144,7 +1144,7 @@ int __kvm_set_memory_region(struct kvm *kvm, > new.dirty_bitmap = NULL; > > r = -ENOMEM; > - if (change == KVM_MR_CREATE) { > + if (change == KVM_MR_CREATE || change == KVM_MR_MOVE) { > new.userspace_addr = mem->userspace_addr; > > if (kvm_arch_create_memslot(kvm, &new, npages)) No, because other architectures don't need to re-allocate new metadata on MOVE and rely on __kvm_set_memory_region() to copy @arch from old to new, e.g. see kvmppc_core_create_memslot_hv(). That being said, that's effectively what the x86 code looks like once kvm_arch_create_memslot() gets merged into kvm_arch_prepare_memory_region(). > > > return 0; > > } > > > > -- > > 2.24.1 > > > > -- > Peter Xu > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel