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d501f97d96
qemu/hw/virtio
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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
vdpa-dev-pci.c
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-iova-tree.c
vhost-iova-tree.h
vhost-scsi-pci.c
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
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
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
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
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
vhost-user-rng-pci.c
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
vhost-user-vsock-pci.c
vhost-user-vsock.c
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
vhost-vsock.c
vhost.c vhost: fix the fd leak 2023-08-03 16:06:49 -04:00
virtio-9p-pci.c
virtio-balloon-pci.c
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
virtio-bus.c
virtio-config-io.c
virtio-crypto-pci.c
virtio-crypto.c hw/other: spelling fixes 2023-09-21 11:31:16 +03:00
virtio-hmp-cmds.c
virtio-input-host-pci.c
virtio-input-pci.c virtio-input-pci: add virtio-multitouch-pci 2023-05-28 13:08:25 +04:00
virtio-iommu-pci.c
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
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.c
virtio-scsi-pci.c
virtio-serial-pci.c
virtio-stub.c
virtio.c virtio: remove unnecessary thread fence while reading next descriptor 2023-10-04 18:15:06 -04:00