Re: How to extend QEMU's vhost-user tests after implementing vhost-user-blk device backend

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, Nov 13, 2019 at 05:23:46PM +0800, Coiby Xu wrote:
> I've implemented vhost-user-blk device backend by following
> https://wiki.qemu.org/Google_Summer_of_Code_2019#vhost-user-blk_device_backend.
> But I'm not sure what kind of tests I should write or to extend to
> take advantage of implemented vhost-user-blk device backend. The
> existing two tests related to vhost user are tests/vhost-user-bridge.c
> and tests/vhost-user-test.c both of which act as vhost user server to
> test QEMU's implementation of vhost user client. Am I supposed to
> extend these two tests? Could you elaborate on the final step "Extend
> QEMU's vhost-user tests to take advantage of your vhost-user-blk
> device backend"?

Hi Coiby,
The following tests/virtio-blk-test.c test cases will also work with
vhost-user-blk: basic, indirect, idx, nxvirtq.  The other test cases
may require more work because they send QMP commands like block_resize
or device_add virtio-blk-pci.

In theory block_resize should work because the vhost-user-blk device
backend can send a VIRTIO Configuration Space changed interrupt
(VHOST_USER_SLAVE_CONFIG_CHANGE_MSG), but I haven't checked if this code
path is fully implemented.

In order to reuse existing test cases you could add new initialization
code to virtio-blk-test.c that:
1. Starts the vhost-user-blk device backend
2. Adds a -device vhost-user-blk-pci connected to that device backend

Please post your patches to qemu-devel even if you don't have test cases
yet.  That way you can get review feedback earlier.

Stefan

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