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Tsirkin" To: Cindy Lu Cc: jasowang@redhat.com, qemu-devel@nongnu.org, philmd@linaro.org, qemu-stable@nongnu.org Subject: Re: [PATCH v3] virtio-pci: Fix the use of an uninitialized irqfd Message-ID: <20240627045416-mutt-send-email-mst@kernel.org> References: <20240626024434.10523-1-lulu@redhat.com> <20240626033920-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.207, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Jun 27, 2024 at 04:40:33PM +0800, Cindy Lu wrote: > On Wed, Jun 26, 2024 at 3:45 PM Michael S. Tsirkin wrote: > > > > On Wed, Jun 26, 2024 at 10:44:31AM +0800, Cindy Lu wrote: > > > The crash was reported in MAC OS and NixOS, here is the link for this bug > > > https://gitlab.com/qemu-project/qemu/-/issues/2334 > > > https://gitlab.com/qemu-project/qemu/-/issues/2321 > > > > > > The root cause is the function virtio_pci_set_guest_notifiers() was not called > > > in the virtio_input device.So the vector_irqfd was not initialized > > > > > > So the fix is add the check for vector_irqfd. > > > > > > Change in V3 > > > > Changelog belongs after --- > > > thanks micheal, will fix this > > > 1) Move the vector_irqfd check to virtio_pci_get_notifier(). > > > The function virtio_pci_get_notifier() can also be used while vdev->status > > > is not VIRTIO_CONFIG_S_DRIVER_OK. In that case, the vector_irqfd could be NULL, > > > so also add the status check here. > > > 2) Add the return value check for kvm_virtio_pci_vector_use_one(). > > > Since the return value of function virtio_pci_set_vector() is void, > > > just add the error message here. > > > > > > This fix is verified in vyatta,MacOS,NixOS,fedora system. > > > > > > The bt tree for this bug is: > > > Thread 6 "CPU 0/KVM" received signal SIGSEGV, Segmentation fault. > > > [Switching to Thread 0x7c817be006c0 (LWP 1269146)] > > > kvm_virtio_pci_vq_vector_use () at ../qemu-9.0.0/hw/virtio/virtio-pci.c:817 > > > 817 if (irqfd->users == 0) { > > > (gdb) thread apply all bt > > > ... > > > Thread 6 (Thread 0x7c817be006c0 (LWP 1269146) "CPU 0/KVM"): > > > 0 kvm_virtio_pci_vq_vector_use () at ../qemu-9.0.0/hw/virtio/virtio-pci.c:817 > > > 1 kvm_virtio_pci_vector_use_one () at ../qemu-9.0.0/hw/virtio/virtio-pci.c:893 > > > 2 0x00005983657045e2 in memory_region_write_accessor () at ../qemu-9.0.0/system/memory.c:497 > > > 3 0x0000598365704ba6 in access_with_adjusted_size () at ../qemu-9.0.0/system/memory.c:573 > > > 4 0x0000598365705059 in memory_region_dispatch_write () at ../qemu-9.0.0/system/memory.c:1528 > > > 5 0x00005983659b8e1f in flatview_write_continue_step.isra.0 () at ../qemu-9.0.0/system/physmem.c:2713 > > > 6 0x000059836570ba7d in flatview_write_continue () at ../qemu-9.0.0/system/physmem.c:2743 > > > 7 flatview_write () at ../qemu-9.0.0/system/physmem.c:2774 > > > 8 0x000059836570bb76 in address_space_write () at ../qemu-9.0.0/system/physmem.c:2894 > > > 9 0x0000598365763afe in address_space_rw () at ../qemu-9.0.0/system/physmem.c:2904 > > > 10 kvm_cpu_exec () at ../qemu-9.0.0/accel/kvm/kvm-all.c:2917 > > > 11 0x000059836576656e in kvm_vcpu_thread_fn () at ../qemu-9.0.0/accel/kvm/kvm-accel-ops.c:50 > > > 12 0x0000598365926ca8 in qemu_thread_start () at ../qemu-9.0.0/util/qemu-thread-posix.c:541 > > > 13 0x00007c8185bcd1cf in ??? () at /usr/lib/libc.so.6 > > > 14 0x00007c8185c4e504 in clone () at /usr/lib/libc.so.6 > > > > > > Fixes: 2ce6cff94d ("virtio-pci: fix use of a released vector") > > > Cc: qemu-stable@nongnu.org > > > > > > > all trailers including s.o.b. should be together, with no empty lines > > > will change this > > > Signed-off-by: Cindy Lu > > > --- > > > hw/virtio/virtio-pci.c | 9 ++++++++- > > > 1 file changed, 8 insertions(+), 1 deletion(-) > > > > > > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c > > > index b1d02f4b3d..87307b9061 100644 > > > --- a/hw/virtio/virtio-pci.c > > > +++ b/hw/virtio/virtio-pci.c > > > @@ -860,6 +860,11 @@ static int virtio_pci_get_notifier(VirtIOPCIProxy *proxy, int queue_no, > > > VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus); > > > VirtQueue *vq; > > > > > > + if ((proxy->vector_irqfd == NULL) && > > > > Preferable: > > if (!proxy->vector_irqfd && > > > > and brackets not really needed here > > > > > > > + (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) { > > > > brackets not really needed here > > > sure, will fix this > > > + return -1; > > > + } > > > + > > > if (queue_no == VIRTIO_CONFIG_IRQ_IDX) { > > > *n = virtio_config_get_guest_notifier(vdev); > > > *vector = vdev->config_vector; > > > @@ -1452,7 +1457,9 @@ static void virtio_pci_set_vector(VirtIODevice *vdev, > > > } > > > /* If the new vector changed need to set it up. */ > > > if (kvm_irqfd && new_vector != VIRTIO_NO_VECTOR) { > > > - kvm_virtio_pci_vector_use_one(proxy, queue_no); > > > + if (kvm_virtio_pci_vector_use_one(proxy, queue_no)) { > > > + virtio_error(vdev, "fail to set the vector %d", new_vector); failed. and print errno? > > > + } > > > } > > > } > > > > > > Is this an unrelated fix? > > > this is for last version's comment, there is an return value for > function kvm_virtio_pci_vector_use_one, but > we can do nothing here, so I just add an erorr message > Thanks > cindy I'd make it a separate patch, documenting in the commit log what is going on. > > > > > > -- > > > 2.45.0 > >