Re: [Xen-devel] [PATCH] xen: remove size limit of privcmd-buf mapping interface

[Jan Beulich]

>>> Juergen Gross <jgross@xxxxxxxx> 11/01/18 1:34 PM >>>
>Currently the size of hypercall buffers allocated via
>/dev/xen/hypercall is limited to a default of 64 memory pages. For live
>migration of guests this might be too small as the page dirty bitmask
>needs to be sized according to the size of the guest. This means
>migrating a 8GB sized guest is already exhausting the default buffer
>size for the dirty bitmap.
>
>There is no sensible way to set a sane limit, so just remove it
>completely. The device node's usage is limited to root anyway, so there
>is no additional DOS scenario added by allowing unlimited buffers.

But is this setting of permissions what we want long term? What about a
de-privileged qemu, which still needs to be able to issue at least dm-op
hypercalls?

Jan