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Re: [PATCH] vhost: don't set vring call if no enabled msix
From: |
Michael S. Tsirkin |
Subject: |
Re: [PATCH] vhost: don't set vring call if no enabled msix |
Date: |
Tue, 9 Apr 2024 05:31:11 -0400 |
On Mon, Apr 08, 2024 at 02:08:42PM +0800, lyx634449800 wrote:
> When conducting performance testing using testpmd in the guest os,
> it was observed that the performance was lower compared to the
> scenario of direct vfio-pci usage.
>
> In the virtual machine operating system, even if the virtio device
> does not use msix interrupts, vhost still sets vring call fd. This
> leads to unnecessary performance overhead. If the guest driver does
> not enable msix capability (e.g virtio-net pmd), we should also
> check and clear the vring call fd.
>
> Signed-off-by: Yuxue Liu <yuxue.liu@jaguarmicro.com>
Fails testing under cross-i686-tci:
https://gitlab.com/mstredhat/qemu/-/jobs/6578881990
36/258 qemu:qtest+qtest-i386 / qtest-i386/ioh3420-test OK
0.15s 1 subtests passed
▶ 37/258 ERROR:../tests/qtest/qos-test.c:191:subprocess_run_one_test: child
process
(/aarch64/virt/generic-pcihost/pci-bus-generic/pci-bus/virtio-net-pci/virtio-net/virtio-net-tests/vhost-user/migrate/subprocess
[22197]) failed unexpectedly ERROR
38/258 qemu:qtest+qtest-i386 / qtest-i386/lpc-ich9-test OK
0.16s 1 subtests passed
37/258 qemu:qtest+qtest-aarch64 / qtest-aarch64/qos-test
ERROR 13.20s killed by signal 6 SIGABRT
>>> G_TEST_DBUS_DAEMON=/builds/mstredhat/qemu/tests/dbus-vmstate-daemon.sh
>>> PYTHON=/builds/mstredhat/qemu/build/pyvenv/bin/python3 MALLOC_PERTURB_=144
>>> QTEST_QEMU_BINARY=./qemu-system-aarch64
>>> /builds/mstredhat/qemu/build/tests/qtest/qos-test --tap -k
――――――――――――――――――――――――――――――――――――― ✀ ―――――――――――――――――――――――――――――――――――――
stderr:
**
ERROR:../tests/qtest/vhost-user-test.c:468:chr_read: assertion failed (err ==
NULL): Bad file descriptor (g-unix-error-quark, 0)
**
ERROR:../tests/qtest/qos-test.c:191:subprocess_run_one_test: child process
(/aarch64/virt/generic-pcihost/pci-bus-generic/pci-bus/virtio-net-pci/virtio-net/virtio-net-tests/vhost-user/migrate/subprocess
[22197]) failed unexpectedly
(test program exited with status code -6)
――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
> ---
> hw/virtio/vhost.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index f50180e60e..b972c84e67 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -1266,13 +1266,15 @@ int vhost_virtqueue_start(struct vhost_dev *dev,
> vhost_virtqueue_mask(dev, vdev, idx, false);
> }
>
> - if (k->query_guest_notifiers &&
> - k->query_guest_notifiers(qbus->parent) &&
> - virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR) {
> - file.fd = -1;
> - r = dev->vhost_ops->vhost_set_vring_call(dev, &file);
> - if (r) {
> - goto fail_vector;
> + if (k->query_guest_notifiers) {
> + if (!k->query_guest_notifiers(qbus->parent) ||
> + (k->query_guest_notifiers(qbus->parent) &&
> + virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR)) {
> + file.fd = -1;
> + r = dev->vhost_ops->vhost_set_vring_call(dev, &file);
> + if (r) {
> + goto fail_vector;
> + }
> }
> }
>
> --
> 2.43.0