[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] question about memory allocation for driver domain

On 09/02/2015 20:02, Oleksandr Tyshchenko wrote:
On Mon, Feb 9, 2015 at 10:31 AM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
On 07/02/2015 01:15, Oleksandr Tyshchenko wrote:
Hi Julien

Hi Oleksandr,

On Thu, Feb 5, 2015 at 6:36 PM, Oleksandr Tyshchenko

The next problem is ballooning. When the guest balloon out memory, the page
will be freed by Xen and can be re-used by another domain.

When guest balloon in, Xen will allocate a page (randomly) and therefore the
mapping won't be anymore IPA (guest physical address) == PA (physical
address). Any DMA request using this address will read/write data from wrong
Is it possible to disable ballon driver for domd?

I think updating is_domain_direct_mapped is enough here.

We won't support memory hotplug for this kind of domain.

The last problem but not the least is, depending on which backend you are
running in the 1:1 domain (such blkback), grant won't be mapped 1:1 to the
guest, so you will have to use swiotlb in order to use the right DMA
address. For instance, without swiotlb, guest won't be able to use a disk
partition via blkfront. This because the backend is giving directly the
grant address to the block driver. To solve this, we have to use swiotlb and
set specific DMA callback. For now, there are only used for DOM0.
We are using SWIOTLB for domd too.

Good :).


Julien Grall

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.