Comment 0 for bug 1887525

[impact]

the impact is the same as bug 1886704, the qemu vhost-user driver fails to init. see that bug for more details on the impact.

[test case]

start a qemu guest with at least one vhost-user interface, and more than 8 discontiguous memory regions. The vhost-user device will fail to init due to exceeding its max memory region limit.

[regression potential]

as this causes vhost-user to ignore some mem regions, any regression would likely involve problems with the vhost-user interface; possibly failure to init the interface, or failure to configure the interface, or problems while using the interface.

[scope]

TBD

[other info]

this is closely related to bug 1886704, but that bug is specifically about the 8 mem region limit of the vhost-user api. This bug doesn't attempt to fix that limitation (as it requires using a new extension of the vhost-user api to increase the max mem regions), this only backports existing upstream patches that fix the vhost region calculations and allow the vhost-user driver to indicate which mem regions it doesn't need to use, so those are ignored, in order to keep the total under the vhost-user limit.