qemu/hw/virtio
Ilya Maximets d501f97d96 virtio: remove unnecessary thread fence while reading next descriptor
It was supposed to be a compiler barrier and it was a compiler barrier
initially called 'wmb' when virtio core support was introduced.
Later all the instances of 'wmb' were switched to smp_wmb to fix memory
ordering issues on non-x86 platforms.  However, this one doesn't need
to be an actual barrier, as its only purpose was to ensure that the
value is not read twice.

And since commit aa570d6fb6 ("virtio: combine the read of a descriptor")
there is no need for a barrier at all, since we're no longer reading
guest memory here, but accessing a local structure.

Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Message-Id: <20230927140016.2317404-2-i.maximets@ovn.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2023-10-04 18:15:06 -04:00
..
Kconfig virtio-md-pci: New parent type for virtio-mem-pci and virtio-pmem-pci 2023-07-12 09:27:25 +02:00
meson.build virtio: add vhost-user-base and a generic vhost-user-device 2023-10-04 04:54:04 -04:00
trace-events vdpa: export vhost_vdpa_set_vring_ready 2023-10-04 04:54:19 -04:00
trace.h trace: switch position of headers to what Meson requires 2020-08-21 06:18:24 -04:00
vdpa-dev-pci.c vdpa: add vdpa-dev-pci support 2022-12-21 06:35:28 -05:00
vdpa-dev.c vdpa: move vhost_vdpa_set_vring_ready to the caller 2023-10-04 04:54:21 -04:00
vhost-backend.c vhost: add method vhost_set_vring_err 2022-06-27 18:53:18 -04:00
vhost-iova-tree.c util: accept iova_tree_remove_parameter by value 2022-09-02 10:22:39 +08:00
vhost-iova-tree.h util: accept iova_tree_remove_parameter by value 2022-09-02 10:22:39 +08:00
vhost-scsi-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
vhost-shadow-virtqueue.c vhost: Add count argument to vhost_svq_poll() 2023-10-04 04:54:23 -04:00
vhost-shadow-virtqueue.h vhost: Add count argument to vhost_svq_poll() 2023-10-04 04:54:23 -04:00
vhost-stub.c vhost: register and change IOMMU flag depending on Device-TLB state 2023-07-10 15:07:50 -04:00
vhost-user-blk-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
vhost-user-device-pci.c virtio: add vhost-user-base and a generic vhost-user-device 2023-10-04 04:54:04 -04:00
vhost-user-device.c hw/virtio: add config support to vhost-user-device 2023-10-04 04:54:05 -04:00
vhost-user-fs-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
vhost-user-fs.c hw/virtio: fix typo in VIRTIO_CONFIG_IRQ_IDX comments 2023-07-10 18:59:32 -04:00
vhost-user-gpio-pci.c hw/virtio: add vhost-user-gpio-pci boilerplate 2022-10-07 09:41:51 -04:00
vhost-user-gpio.c qmp: update virtio feature maps, vhost-user-gpio introspection 2023-10-04 04:54:26 -04:00
vhost-user-i2c-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
vhost-user-i2c.c virtio: i2c: Check notifier helpers for VIRTIO_CONFIG_IRQ_IDX 2023-04-24 22:56:55 -04:00
vhost-user-input-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
vhost-user-rng-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
vhost-user-rng.c vhost-user-rng: Back up vqs before cleaning up vhost_dev 2023-03-02 03:10:47 -05:00
vhost-user-scmi-pci.c hw/virtio: Add vhost-user-scmi-pci boilerplate 2023-07-10 16:17:08 -04:00
vhost-user-scmi.c hw/virtio: Add a protection against duplicate vu_scmi_stop calls 2023-08-03 16:06:49 -04:00
vhost-user-scsi-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
vhost-user-vsock-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
vhost-user-vsock.c hw/virtio: introduce virtio_device_should_start 2022-11-07 14:08:18 -05:00
vhost-user.c vhost-user: move VhostUserProtocolFeature definition to header file 2023-10-04 04:54:28 -04:00
vhost-vdpa.c vdpa: move vhost_vdpa_set_vring_ready to the caller 2023-10-04 04:54:21 -04:00
vhost-vsock-common.c hw/virtio: fix typo in VIRTIO_CONFIG_IRQ_IDX comments 2023-07-10 18:59:32 -04:00
vhost-vsock-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
vhost-vsock.c hw/virtio: introduce virtio_device_should_start 2022-11-07 14:08:18 -05:00
vhost.c vhost: fix the fd leak 2023-08-03 16:06:49 -04:00
virtio-9p-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
virtio-balloon-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
virtio-balloon.c hw: replace most qemu_bh_new calls with qemu_bh_new_guarded 2023-04-28 11:31:54 +02:00
virtio-blk-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
virtio-bus.c virtio: stop ioeventfd on reset 2022-06-14 16:50:30 +02:00
virtio-config-io.c hw/virtio: Extract config read/write accessors to virtio-config-io.c 2022-12-21 07:32:24 -05:00
virtio-crypto-pci.c Use DECLARE_*CHECKER* macros 2020-09-09 09:27:09 -04:00
virtio-crypto.c hw/other: spelling fixes 2023-09-21 11:31:16 +03:00
virtio-hmp-cmds.c virtio: Move HMP commands from monitor/ to hw/virtio/ 2023-02-04 07:56:54 +01:00
virtio-input-host-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
virtio-input-pci.c virtio-input-pci: add virtio-multitouch-pci 2023-05-28 13:08:25 +04:00
virtio-iommu-pci.c hw/virtio/virtio-iommu-pci: Enforce the device is plugged on the root bus 2022-11-07 13:12:19 -05:00
virtio-iommu.c virtio-iommu: Standardize granule extraction and formatting 2023-08-03 16:06:49 -04:00
virtio-md-pci.c virtio-md-pci: Support unplug requests for compatible devices 2023-07-12 09:27:30 +02:00
virtio-mem-pci.c virtio-mem-pci: Device unplug support 2023-07-12 09:27:32 +02:00
virtio-mem-pci.h virtio-md-pci: New parent type for virtio-mem-pci and virtio-pmem-pci 2023-07-12 09:27:25 +02:00
virtio-mem.c hw/other: spelling fixes 2023-09-21 11:31:16 +03:00
virtio-mmio.c virtio: refresh vring region cache after updating a virtqueue size 2023-04-21 03:08:21 -04:00
virtio-net-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
virtio-pci.c virtio-pci: add handling of PCI ATS and Device-TLB enable/disable 2023-05-19 10:30:46 -04:00
virtio-pmem-pci.c virtio-md-pci: New parent type for virtio-mem-pci and virtio-pmem-pci 2023-07-12 09:27:25 +02:00
virtio-pmem-pci.h virtio-md-pci: New parent type for virtio-mem-pci and virtio-pmem-pci 2023-07-12 09:27:25 +02:00
virtio-pmem.c thread-pool: avoid passing the pool parameter every time 2023-04-25 13:17:28 +02:00
virtio-qmp.c vhost-user: move VhostUserProtocolFeature definition to header file 2023-10-04 04:54:28 -04:00
virtio-qmp.h qmp: remove virtio_list, search QOM tree instead 2023-10-04 04:54:24 -04:00
virtio-rng-pci.c virtio-rng-pci: Allow setting nvectors, so we can use MSI-X 2022-11-07 13:12:20 -05:00
virtio-rng.c virtio: drop name parameter for virtio_init() 2022-05-16 04:38:40 -04:00
virtio-scsi-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
virtio-serial-pci.c hw/virtio: move virtio-pci.h into shared include space 2022-05-16 04:38:40 -04:00
virtio-stub.c qmp: add QMP command x-query-virtio-queue-element 2022-10-09 16:38:45 -04:00
virtio.c virtio: remove unnecessary thread fence while reading next descriptor 2023-10-04 18:15:06 -04:00