From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753365Ab2A3SYm (ORCPT ); Mon, 30 Jan 2012 13:24:42 -0500 Received: from goliath.siemens.de ([192.35.17.28]:28579 "EHLO goliath.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752595Ab2A3SYl (ORCPT ); Mon, 30 Jan 2012 13:24:41 -0500 Message-ID: <4F26E063.5020207@siemens.com> Date: Mon, 30 Jan 2012 19:24:35 +0100 From: Jan Kiszka User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 MIME-Version: 1.0 To: Alex Williamson CC: "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] KVM: Fix assigned device MSI-X entry setting leak References: <20120130180540.17524.62489.stgit@bling.home> In-Reply-To: <20120130180540.17524.62489.stgit@bling.home> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2012-01-30 19:06, Alex Williamson wrote: > We need to prioritize our matching when setting MSI-X vector > entries. Unused entries should only be used if we don't find > an exact match or else we risk duplicating entries. This was > causing an ENOSPC return when trying to mask and unmask MSI-X > vectors based on guest MSI-X table updates. > > Signed-off-by: Alex Williamson > > --- > > The faulting sequence went something like: > > Start: > [0] entry 0, vector A > [1] entry 1, vector B > [2] entry 2, vector C > > Set entry 1 to 0: > [0] entry 0, vector A > [1] entry 1->1, vector B->0 > [2] entry 2, vector C > > Set entry 2 to 0: > [0] entry 0, vector A > [1] entry 1->2, vector 0->0 <- incorrectly matched > [2] entry 2, vector C > > Set entry 2 to C: > [0] entry 0, vector A > [1] entry 2->2, vector 0->C <- incorrectly matched again > [2] entry 2, vector C > > Set entry 1 to B: > [0] entry 0, vector A > [1] entry 2, vector C > [2] entry 2, vector C > -ENOSPC > > Userspace will need to test for this bug (or do we want to set > a feature flag?). The latter is much simpler. We did it before. > > virt/kvm/assigned-dev.c | 21 +++++++++++++++------ > 1 files changed, 15 insertions(+), 6 deletions(-) > > diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c > index 758e3b3..798a090 100644 > --- a/virt/kvm/assigned-dev.c > +++ b/virt/kvm/assigned-dev.c > @@ -728,7 +728,7 @@ msix_nr_out: > static int kvm_vm_ioctl_set_msix_entry(struct kvm *kvm, > struct kvm_assigned_msix_entry *entry) > { > - int r = 0, i; > + int r = 0, i, unused = -1; > struct kvm_assigned_dev_kernel *adev; > > mutex_lock(&kvm->lock); > @@ -741,17 +741,26 @@ static int kvm_vm_ioctl_set_msix_entry(struct kvm *kvm, > goto msix_entry_out; > } > > - for (i = 0; i < adev->entries_nr; i++) > - if (adev->guest_msix_entries[i].vector == 0 || > - adev->guest_msix_entries[i].entry == entry->entry) { > + for (i = 0; i < adev->entries_nr; i++) { > + if (unused < 0 && !adev->guest_msix_entries[i].vector) > + unused = i; > + > + if (adev->guest_msix_entries[i].entry == entry->entry) { > adev->guest_msix_entries[i].entry = entry->entry; > adev->guest_msix_entries[i].vector = entry->gsi; > adev->host_msix_entries[i].entry = entry->entry; > break; > } > + } > + > if (i == adev->entries_nr) { > - r = -ENOSPC; > - goto msix_entry_out; > + if (unused < 0) { > + r = -ENOSPC; > + goto msix_entry_out; > + } > + adev->guest_msix_entries[unused].entry = entry->entry; > + adev->guest_msix_entries[unused].vector = entry->gsi; > + adev->host_msix_entries[unused].entry = entry->entry; > } > > msix_entry_out: > Looks good. Does it fix the masking problems? Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux