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* vp_vdpa: don't allocate unused msix vectorsYuxue Liu2024-05-221-6/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When there is a ctlq and it doesn't require interrupt callbacks,the original method of calculating vectors wastes hardware msi or msix resources as well as system IRQ resources. When conducting performance testing using testpmd in the guest os, it was found that the performance was lower compared to directly using vfio-pci to passthrough the device In scenarios where the virtio device in the guest os does not utilize interrupts, the vdpa driver still configures the hardware's msix vector. Therefore, the hardware still sends interrupts to the host os. Because of this unnecessary action by the hardware, hardware performance decreases, and it also affects the performance of the host os. Before modification:(interrupt mode) 32: 0 0 0 0 PCI-MSI 32768-edge vp-vdpa[0000:00:02.0]-0 33: 0 0 0 0 PCI-MSI 32769-edge vp-vdpa[0000:00:02.0]-1 34: 0 0 0 0 PCI-MSI 32770-edge vp-vdpa[0000:00:02.0]-2 35: 0 0 0 0 PCI-MSI 32771-edge vp-vdpa[0000:00:02.0]-config After modification:(interrupt mode) 32: 0 0 1 7 PCI-MSI 32768-edge vp-vdpa[0000:00:02.0]-0 33: 36 0 3 0 PCI-MSI 32769-edge vp-vdpa[0000:00:02.0]-1 34: 0 0 0 0 PCI-MSI 32770-edge vp-vdpa[0000:00:02.0]-config Before modification:(virtio pmd mode for guest os) 32: 0 0 0 0 PCI-MSI 32768-edge vp-vdpa[0000:00:02.0]-0 33: 0 0 0 0 PCI-MSI 32769-edge vp-vdpa[0000:00:02.0]-1 34: 0 0 0 0 PCI-MSI 32770-edge vp-vdpa[0000:00:02.0]-2 35: 0 0 0 0 PCI-MSI 32771-edge vp-vdpa[0000:00:02.0]-config After modification:(virtio pmd mode for guest os) 32: 0 0 0 0 PCI-MSI 32768-edge vp-vdpa[0000:00:02.0]-config To verify the use of the virtio PMD mode in the guest operating system, the following patch needs to be applied to QEMU: https://lore.kernel.org/all/20240408073311.2049-1-yuxue.liu@jaguarmicro.com Signed-off-by: Yuxue Liu <yuxue.liu@jaguarmicro.com> Acked-by: Jason Wang <jasowang@redhat.com> Reviewed-by: Heng Qi <hengqi@linux.alibaba.com> Message-Id: <20240410033020.1310-1-yuxue.liu@jaguarmicro.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vp_vdpa: Fix return value check vp_vdpa_request_irqYuxue Liu2024-05-221-1/+4
| | | | | | | | | | | In the vp_vdpa_set_status function, when setting the device status to VIRTIO_CONFIG_S_DRIVER_OK, the vp_vdpa_request_irq function may fail. In such cases, the device status should not be set to DRIVER_OK. Add exception printing to remind the user. Signed-off-by: Yuxue Liu <yuxue.liu@jaguarmicro.com> Message-Id: <20240325105448.235-1-gavin.liu@jaguarmicro.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vp_vdpa: implement vdpa_config_ops.get_vq_sizeZhu Lingshan2024-03-191-0/+8
| | | | | | | | | This commit implements vdpa_config_ops.get_vq_size in vp_vdpa, which reports per virtqueue size. Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com> Message-Id: <20240202163905.8834-5-lingshan.zhu@intel.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vp_vdpa: fix the crash in hot unplug with vp_vdpaCindy Lu2023-03-101-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | While unplugging the vp_vdpa device, it triggers a kernel panic The root cause is: vdpa_mgmtdev_unregister() will accesses modern devices which will cause a use after free. So need to change the sequence in vp_vdpa_remove [ 195.003359] BUG: unable to handle page fault for address: ff4e8beb80199014 [ 195.004012] #PF: supervisor read access in kernel mode [ 195.004486] #PF: error_code(0x0000) - not-present page [ 195.004960] PGD 100000067 P4D 1001b6067 PUD 1001b7067 PMD 1001b8067 PTE 0 [ 195.005578] Oops: 0000 1 PREEMPT SMP PTI [ 195.005968] CPU: 13 PID: 164 Comm: kworker/u56:10 Kdump: loaded Not tainted 5.14.0-252.el9.x86_64 #1 [ 195.006792] Hardware name: Red Hat KVM/RHEL, BIOS edk2-20221207gitfff6d81270b5-2.el9 unknown [ 195.007556] Workqueue: kacpi_hotplug acpi_hotplug_work_fn [ 195.008059] RIP: 0010:ioread8+0x31/0x80 [ 195.008418] Code: 77 28 48 81 ff 00 00 01 00 76 0b 89 fa ec 0f b6 c0 c3 cc cc cc cc 8b 15 ad 72 93 01 b8 ff 00 00 00 85 d2 75 0f c3 cc cc cc cc <8a> 07 0f b6 c0 c3 cc cc cc cc 83 ea 01 48 83 ec 08 48 89 fe 48 c7 [ 195.010104] RSP: 0018:ff4e8beb8067bab8 EFLAGS: 00010292 [ 195.010584] RAX: ffffffffc05834a0 RBX: ffffffffc05843c0 RCX: ff4e8beb8067bae0 [ 195.011233] RDX: ff1bcbd580f88000 RSI: 0000000000000246 RDI: ff4e8beb80199014 [ 195.011881] RBP: ff1bcbd587e39000 R08: ffffffff916fa2d0 R09: ff4e8beb8067ba68 [ 195.012527] R10: 000000000000001c R11: 0000000000000000 R12: ff1bcbd5a3de9120 [ 195.013179] R13: ffffffffc062d000 R14: 0000000000000080 R15: ff1bcbe402bc7805 [ 195.013826] FS: 0000000000000000(0000) GS:ff1bcbe402740000(0000) knlGS:0000000000000000 [ 195.014564] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 195.015093] CR2: ff4e8beb80199014 CR3: 0000000107dea002 CR4: 0000000000771ee0 [ 195.015741] PKRU: 55555554 [ 195.016001] Call Trace: [ 195.016233] <TASK> [ 195.016434] vp_modern_get_status+0x12/0x20 [ 195.016823] vp_vdpa_reset+0x1b/0x50 [vp_vdpa] [ 195.017238] virtio_vdpa_reset+0x3c/0x48 [virtio_vdpa] [ 195.017709] remove_vq_common+0x1f/0x3a0 [virtio_net] [ 195.018178] virtnet_remove+0x5d/0x70 [virtio_net] [ 195.018618] virtio_dev_remove+0x3d/0x90 [ 195.018986] device_release_driver_internal+0x1aa/0x230 [ 195.019466] bus_remove_device+0xd8/0x150 [ 195.019841] device_del+0x18b/0x3f0 [ 195.020167] ? kernfs_find_ns+0x35/0xd0 [ 195.020526] device_unregister+0x13/0x60 [ 195.020894] unregister_virtio_device+0x11/0x20 [ 195.021311] device_release_driver_internal+0x1aa/0x230 [ 195.021790] bus_remove_device+0xd8/0x150 [ 195.022162] device_del+0x18b/0x3f0 [ 195.022487] device_unregister+0x13/0x60 [ 195.022852] ? vdpa_dev_remove+0x30/0x30 [vdpa] [ 195.023270] vp_vdpa_dev_del+0x12/0x20 [vp_vdpa] [ 195.023694] vdpa_match_remove+0x2b/0x40 [vdpa] [ 195.024115] bus_for_each_dev+0x78/0xc0 [ 195.024471] vdpa_mgmtdev_unregister+0x65/0x80 [vdpa] [ 195.024937] vp_vdpa_remove+0x23/0x40 [vp_vdpa] [ 195.025353] pci_device_remove+0x36/0xa0 [ 195.025719] device_release_driver_internal+0x1aa/0x230 [ 195.026201] pci_stop_bus_device+0x6c/0x90 [ 195.026580] pci_stop_and_remove_bus_device+0xe/0x20 [ 195.027039] disable_slot+0x49/0x90 [ 195.027366] acpiphp_disable_and_eject_slot+0x15/0x90 [ 195.027832] hotplug_event+0xea/0x210 [ 195.028171] ? hotplug_event+0x210/0x210 [ 195.028535] acpiphp_hotplug_notify+0x22/0x80 [ 195.028942] ? hotplug_event+0x210/0x210 [ 195.029303] acpi_device_hotplug+0x8a/0x1d0 [ 195.029690] acpi_hotplug_work_fn+0x1a/0x30 [ 195.030077] process_one_work+0x1e8/0x3c0 [ 195.030451] worker_thread+0x50/0x3b0 [ 195.030791] ? rescuer_thread+0x3a0/0x3a0 [ 195.031165] kthread+0xd9/0x100 [ 195.031459] ? kthread_complete_and_exit+0x20/0x20 [ 195.031899] ret_from_fork+0x22/0x30 [ 195.032233] </TASK> Fixes: ffbda8e9df10 ("vdpa/vp_vdpa : add vdpa tool support in vp_vdpa") Tested-by: Lei Yang <leiyang@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Cindy Lu <lulu@redhat.com> Message-Id: <20230214080924.131462-1-lulu@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com>
* vdpa/vp_vdpa: fix kfree a wrong pointer in vp_vdpa_removeRong Wang2022-12-281-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In vp_vdpa_remove(), the code kfree(&vp_vdpa_mgtdev->mgtdev.id_table) uses a reference of pointer as the argument of kfree, which is the wrong pointer and then may hit crash like this: Unable to handle kernel paging request at virtual address 00ffff003363e30c Internal error: Oops: 96000004 [#1] SMP Call trace: rb_next+0x20/0x5c ext4_readdir+0x494/0x5c4 [ext4] iterate_dir+0x168/0x1b4 __se_sys_getdents64+0x68/0x170 __arm64_sys_getdents64+0x24/0x30 el0_svc_common.constprop.0+0x7c/0x1bc do_el0_svc+0x2c/0x94 el0_svc+0x20/0x30 el0_sync_handler+0xb0/0xb4 el0_sync+0x160/0x180 Code: 54000220 f9400441 b4000161 aa0103e0 (f9400821) SMP: stopping secondary CPUs Starting crashdump kernel... Fixes: ffbda8e9df10 ("vdpa/vp_vdpa : add vdpa tool support in vp_vdpa") Signed-off-by: Rong Wang <wangrong68@huawei.com> Signed-off-by: Nanyong Sun <sunnanyong@huawei.com> Message-Id: <20221207120813.2837529-1-sunnanyong@huawei.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Cindy Lu <lulu@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com>
* vp_vdpa: support feature provisioningJason Wang2022-10-071-2/+20
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch allows the device features to be provisioned via netlink. This is done by: 1) validating the provisioned features to be a subset of the parent features. 2) clearing the features that is not wanted by the userspace For example: # vdpa mgmtdev show pci/0000:02:00.0: supported_classes net max_supported_vqs 3 dev_features CSUM GUEST_CSUM CTRL_GUEST_OFFLOADS MAC GUEST_TSO4 GUEST_TSO6 GUEST_ECN GUEST_UFO HOST_TSO4 HOST_TSO6 HOST_ECN HOST_UFO MRG_RXBUF STATUS CTRL_VQ CTRL_RX CTRL_VLAN CTRL_RX_EXTRA GUEST_ANNOUNCE CTRL_MAC_ADDR RING_INDIRECT_DESC RING_EVENT_IDX VERSION_1 ACCESS_PLATFORM 1) provision vDPA device with all features that are supported by the virtio-pci # vdpa dev add name dev1 mgmtdev pci/0000:02:00.0 # vdpa dev config show dev1: mac 52:54:00:12:34:56 link up link_announce false mtu 65535 negotiated_features CSUM GUEST_CSUM CTRL_GUEST_OFFLOADS MAC GUEST_TSO4 GUEST_TSO6 GUEST_ECN GUEST_UFO HOST_TSO4 HOST_TSO6 HOST_ECN HOST_UFO MRG_RXBUF STATUS CTRL_VQ CTRL_RX CTRL_VLAN GUEST_ANNOUNCE CTRL_MAC_ADDR RING_INDIRECT_DESC RING_EVENT_IDX VERSION_1 ACCESS_PLATFORM 2) provision vDPA device with a subset of the features # vdpa dev add name dev1 mgmtdev pci/0000:02:00.0 device_features 0x300020000 # dev1: mac 52:54:00:12:34:56 link up link_announce false mtu 65535 negotiated_features CTRL_VQ VERSION_1 ACCESS_PLATFORM Reviewed-by: Eli Cohen <elic@nvidia.com> Signed-off-by: Jason Wang <jasowang@redhat.com> Message-Id: <20220927074810.28627-4-jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vdpa/vp_vdpa : add vdpa tool support in vp_vdpaCindy Lu2022-05-311-32/+129
| | | | | | | | | | | | | | | | | this patch is to add the support for vdpa tool in vp_vdpa here is the example steps modprobe vp_vdpa modprobe vhost_vdpa echo 0000:00:06.0>/sys/bus/pci/drivers/virtio-pci/unbind echo 1af4 1041 > /sys/bus/pci/drivers/vp-vdpa/new_id vdpa dev add name vdpa1 mgmtdev pci/0000:00:06.0 Signed-off-by: Cindy Lu <lulu@redhat.com> Message-Id: <20220429091030.547434-1-lulu@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com>
* vdpa: multiple address spaces supportGautam Dawar2022-05-311-1/+1
| | | | | | | | | | | | | | | | | | | | | | | This patches introduces the multiple address spaces support for vDPA device. This idea is to identify a specific address space via an dedicated identifier - ASID. During vDPA device allocation, vDPA device driver needs to report the number of address spaces supported by the device then the DMA mapping ops of the vDPA device needs to be extended to support ASID. This helps to isolate the environments for the virtqueue that will not be assigned directly. E.g in the case of virtio-net, the control virtqueue will not be assigned directly to guest. As a start, simply claim 1 virtqueue groups and 1 address spaces for all vDPA devices. And vhost-vDPA will simply reject the device with more than 1 virtqueue groups or address spaces. Signed-off-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Gautam Dawar <gdawar@xilinx.com> Message-Id: <20220330180436.24644-7-gdawar@xilinx.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vdpa: introduce virtqueue groupsGautam Dawar2022-05-311-1/+1
| | | | | | | | | | | | This patch introduces virtqueue groups to vDPA device. The virtqueue group is the minimal set of virtqueues that must share an address space. And the address space identifier could only be attached to a specific virtqueue group. Signed-off-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Gautam Dawar <gdawar@xilinx.com> Message-Id: <20220330180436.24644-6-gdawar@xilinx.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vdpa: fix use-after-free on vp_vdpa_removeZhang Min2022-03-061-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When vp_vdpa driver is unbind, vp_vdpa is freed in vdpa_unregister_device and then vp_vdpa->mdev.pci_dev is dereferenced in vp_modern_remove, triggering use-after-free. Call Trace of unbinding driver free vp_vdpa : do_syscall_64 vfs_write kernfs_fop_write_iter device_release_driver_internal pci_device_remove vp_vdpa_remove vdpa_unregister_device kobject_release device_release kfree Call Trace of dereference vp_vdpa->mdev.pci_dev: vp_modern_remove pci_release_selected_regions pci_release_region pci_resource_len pci_resource_end (dev)->resource[(bar)].end Signed-off-by: Zhang Min <zhang.min9@zte.com.cn> Signed-off-by: Yi Wang <wang.yi59@zte.com.cn> Link: https://lore.kernel.org/r/20220301091059.46869-1-wang.yi59@zte.com.cn Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Fixes: 64b9f64f80a6 ("vdpa: introduce virtio pci driver") Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
* vdpa: Provide interface to read driver featuresEli Cohen2022-01-151-4/+12
| | | | | | | | | | | | | | | | | | | | | | Provide an interface to read the negotiated features. This is needed when building the netlink message in vdpa_dev_net_config_fill(). Also fix the implementation of vdpa_dev_net_config_fill() to use the negotiated features instead of the device features. To make APIs clearer, make the following name changes to struct vdpa_config_ops so they better describe their operations: get_features -> get_device_features set_features -> set_driver_features Finally, add get_driver_features to return the negotiated features and add implementation to all the upstream drivers. Acked-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Eli Cohen <elic@nvidia.com> Link: https://lore.kernel.org/r/20220105114646.577224-2-elic@nvidia.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vp_vdpa: add vq irq offloading supportWu Zongyong2021-11-011-0/+12
| | | | | | | | | | This patch implements the get_vq_irq() callback for virtio pci devices to allow irq offloading. Signed-off-by: Wu Zongyong <wuzongyong@linux.alibaba.com> Acked-by: Jason Wang <jasowang@redhat.com> Link: https://lore.kernel.org/r/bb091e5505db704dd620f8854a7aebc921d2a752.1635493219.git.wuzongyong@linux.alibaba.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vdpa: Support transferring virtual addressing during DMA mappingXie Yongji2021-09-061-1/+1
| | | | | | | | | | | | | | | This patch introduces an attribute for vDPA device to indicate whether virtual address can be used. If vDPA device driver set it, vhost-vdpa bus driver will not pin user page and transfer userspace virtual address instead of physical address during DMA mapping. And corresponding vma->vm_file and offset will be also passed as an opaque pointer. Suggested-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Xie Yongji <xieyongji@bytedance.com> Acked-by: Jason Wang <jasowang@redhat.com> Link: https://lore.kernel.org/r/20210831103634.33-11-xieyongji@bytedance.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vdpa: Add reset callback in vdpa_config_opsXie Yongji2021-09-061-2/+13
| | | | | | | | | | This adds a new callback to support device specific reset behavior. The vdpa bus driver will call the reset function instead of setting status to zero during resetting. Signed-off-by: Xie Yongji <xieyongji@bytedance.com> Link: https://lore.kernel.org/r/20210831103634.33-6-xieyongji@bytedance.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vp_vdpa: Fix return value check for vdpa_alloc_device()Xie Yongji2021-08-111-2/+2
| | | | | | | | | | | | | | | The vdpa_alloc_device() returns an error pointer upon failure, not NULL. To handle the failure correctly, this replaces NULL check with IS_ERR() check and propagate the error upwards. Fixes: 64b9f64f80a6 ("vdpa: introduce virtio pci driver") Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Xie Yongji <xieyongji@bytedance.com> Link: https://lore.kernel.org/r/20210715080026.242-2-xieyongji@bytedance.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
* vp_vdpa: allow set vq state to initial state after resetJason Wang2021-07-081-3/+39
| | | | | | | | | | | | | | We used to fail the set_vq_state() since it was not supported yet by the virtio spec. But if the bus tries to set the state which is equal to the device initial state after reset, we can let it go. This is a must for virtio_vdpa() to set vq state during probe which is required for some vDPA parents. Signed-off-by: Jason Wang <jasowang@redhat.com> Link: https://lore.kernel.org/r/20210602021536.39525-4-jasowang@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Eli Cohen <elic@nvidia.com>
* vp_vdpa: correct the return value when fail to map notificationJason Wang2021-07-031-0/+1
| | | | | | | | | | | | | We forget to assign a error value when we fail to map the notification during prove. This patch fixes it. Reported-by: kernel test robot <lkp@intel.com> Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Fixes: 11d8ffed00b23 ("vp_vdpa: switch to use vp_modern_map_vq_notify()") Signed-off-by: Jason Wang <jasowang@redhat.com> Link: https://lore.kernel.org/r/20210624035939.26618-1-jasowang@redhat.com Reviewed-by: Stefano Garzarella <sgarzare@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vdpa: add get_config_size callback in vdpa_config_opsStefano Garzarella2021-05-031-0/+8
| | | | | | | | | | This new callback is used to get the size of the configuration space of vDPA devices. Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> Link: https://lore.kernel.org/r/20210315163450.254396-9-sgarzare@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com>
* vp_vdpa: report doorbell addressJason Wang2021-05-031-1/+17
| | | | | | | | | | | This patch reports the per vq doorbell location and size to vDPA bus. Userspace can then map the doorbell via mmap() via vhost-vDPA bus driver. Signed-off-by: Jason Wang <jasowang@redhat.com> Link: https://lore.kernel.org/r/20210415073147.19331-8-jasowang@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Eli Cohen <elic@nvidia.com>
* virtio-pci library: report resource addressJason Wang2021-05-031-1/+2
| | | | | | | | | | Sometimes it might be useful to report the capability physical address. One example is to report the physical address of the doorbell in order to be mapped by userspace. Signed-off-by: Jason Wang <jasowang@redhat.com> Link: https://lore.kernel.org/r/20210415073147.19331-7-jasowang@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
* vp_vdpa: switch to use vp_modern_map_vq_notify()Jason Wang2021-05-031-4/+5
| | | | | | | | | This patch switches to use vp_vdpa to use vp_modern_map_notify(). Signed-off-by: Jason Wang <jasowang@redhat.com> Link: https://lore.kernel.org/r/20210415073147.19331-4-jasowang@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Eli Cohen <elic@nvidia.com>
* vdpa: introduce virtio pci driverJason Wang2021-05-032-0/+460
This patch introduce a vDPA driver for virtio-pci device. It bridges the virtio-pci control command to the vDPA bus. This will be used for features prototyping and testing. Note that get/restore virtqueue state is not supported which needs extension on the virtio specification. Signed-off-by: Jason Wang <jasowang@redhat.com> Link: https://lore.kernel.org/r/20210223061905.422659-4-jasowang@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>