On Thu, 16 May 2019 08:32:28 +0200 Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > On Wed, 15 May 2019 23:08:17 +0200 > Halil Pasic <pasic@xxxxxxxxxxxxx> wrote: > > > On Tue, 14 May 2019 10:47:34 -0400 > > "Jason J. Herne" <jjherne@xxxxxxxxxxxxx> wrote: > > > > Are we > > > worried that virtio data structures are going to be a burden on the 31-bit address space? > > > > > > > > > > That is a good question I can not answer. Since it is currently at least > > a page per queue (because we use dma direct, right Mimu?), I am concerned > > about this. > > > > Connie, what is your opinion? > > Yes, running into problems there was one of my motivations for my > question. I guess it depends on the number of devices and how many > queues they use. The problem is that it affects not only protected virt > guests, but all guests. > Unless things are about to change only devices that have VIRTIO_F_IOMMU_PLATFORM are affected. So it does not necessarily affect not protected virt guests. (With prot virt we have to use VIRTIO_F_IOMMU_PLATFORM.) If it were not like this, I would be much more worried. @Mimu: Could you please discuss this problem with the team? It might be worth considering to go back to the design of the RFC (i.e. cio/ccw stuff allocated from a common cio dma pool which gives you 31 bit addressable memory, and 64 bit dma mask for a ccw device of a virtio device). Regards, Halil
