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From 5bcbdfefff3209a194168dbe772c7e2f45d248f7 Mon Sep 17 00:00:00 2001
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From: Maxim Levitsky <mlevitsk@redhat.com>
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Date: Sun, 22 Dec 2019 11:02:07 +0100
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Subject: [PATCH 2/7] virtio: Return true from virtio_queue_empty if broken
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RH-Author: Maxim Levitsky <mlevitsk@redhat.com>
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Message-id: <20191222110207.21384-3-mlevitsk@redhat.com>
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Patchwork-id: 93208
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O-Subject: [RHEL-8.2.0 qemu-kvm PATCH 2/2] virtio: Return true from virtio_queue_empty if broken
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Bugzilla: 1769613
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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RH-Acked-by: Peter Xu <peterx@redhat.com>
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From: Fam Zheng <famz@redhat.com>
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Both virtio-blk and virtio-scsi use virtio_queue_empty() as the
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loop condition in VQ handlers (virtio_blk_handle_vq,
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virtio_scsi_handle_cmd_vq). When a device is marked broken in
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virtqueue_pop, for example if a vIOMMU address translation failed, we
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want to break out of the loop.
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This fixes a hanging problem when booting a CentOS 3.10.0-862.el7.x86_64
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kernel with ATS enabled:
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$ qemu-system-x86_64 \
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... \
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-device intel-iommu,intremap=on,caching-mode=on,eim=on,device-iotlb=on \
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-device virtio-scsi-pci,iommu_platform=on,ats=on,id=scsi0,bus=pci.4,addr=0x0
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The dead loop happens immediately when the kernel boots and initializes
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the device, where virtio_scsi_data_plane_handle_cmd will not return:
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> ...
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> #13 0x00005586602b7793 in virtio_scsi_handle_cmd_vq
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> #14 0x00005586602b8d66 in virtio_scsi_data_plane_handle_cmd
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> #15 0x00005586602ddab7 in virtio_queue_notify_aio_vq
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> #16 0x00005586602dfc9f in virtio_queue_host_notifier_aio_poll
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> #17 0x00005586607885da in run_poll_handlers_once
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> #18 0x000055866078880e in try_poll_mode
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> #19 0x00005586607888eb in aio_poll
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> #20 0x0000558660784561 in aio_wait_bh_oneshot
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> #21 0x00005586602b9582 in virtio_scsi_dataplane_stop
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> #22 0x00005586605a7110 in virtio_bus_stop_ioeventfd
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> #23 0x00005586605a9426 in virtio_pci_stop_ioeventfd
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> #24 0x00005586605ab808 in virtio_pci_common_write
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> #25 0x0000558660242396 in memory_region_write_accessor
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> #26 0x00005586602425ab in access_with_adjusted_size
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> #27 0x0000558660245281 in memory_region_dispatch_write
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> #28 0x00005586601e008e in flatview_write_continue
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> #29 0x00005586601e01d8 in flatview_write
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> #30 0x00005586601e04de in address_space_write
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> #31 0x00005586601e052f in address_space_rw
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> #32 0x00005586602607f2 in kvm_cpu_exec
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> #33 0x0000558660227148 in qemu_kvm_cpu_thread_fn
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> #34 0x000055866078bde7 in qemu_thread_start
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> #35 0x00007f5784906594 in start_thread
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> #36 0x00007f5784639e6f in clone
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With this patch, virtio_queue_empty will now return 1 as soon as the
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vdev is marked as broken, after a "virtio: zero sized buffers are not
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allowed" error.
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To be consistent, update virtio_queue_empty_rcu as well.
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Signed-off-by: Fam Zheng <famz@redhat.com>
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Message-Id: <20180910145616.8598-2-famz@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit 2d1df8591022737b8ef19d681ff74eda389f5198)
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Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/virtio/virtio.c | 8 ++++++++
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1 file changed, 8 insertions(+)
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diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
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index 1debb01..fce199e 100644
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--- a/hw/virtio/virtio.c
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+++ b/hw/virtio/virtio.c
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@@ -344,6 +344,10 @@ int virtio_queue_ready(VirtQueue *vq)
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* Called within rcu_read_lock(). */
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static int virtio_queue_empty_rcu(VirtQueue *vq)
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{
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+ if (unlikely(vq->vdev->broken)) {
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+ return 1;
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+ }
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+
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if (unlikely(!vq->vring.avail)) {
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return 1;
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}
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@@ -359,6 +363,10 @@ int virtio_queue_empty(VirtQueue *vq)
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{
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bool empty;
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+ if (unlikely(vq->vdev->broken)) {
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+ return 1;
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+ }
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+
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if (unlikely(!vq->vring.avail)) {
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return 1;
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}
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--
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1.8.3.1
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