[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v2] xen: don't require virtio with grants for non-PV guests
On 16.06.22 08:03, Christoph Hellwig wrote: On Thu, Jun 16, 2022 at 07:37:15AM +0200, Juergen Gross wrote:Commit fa1f57421e0b ("xen/virtio: Enable restricted memory access using Xen grant mappings") introduced a new requirement for using virtio devices: the backend now needs to support the VIRTIO_F_ACCESS_PLATFORM feature. This is an undue requirement for non-PV guests, as those can be operated with existing backends without any problem, as long as those backends are running in dom0. Per default allow virtio devices without grant support for non-PV guests. Add a new config item to always force use of grants for virtio.What Í'd really expect here is to only set the limitations for the actual grant-based devic. Unfortunately PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS is global instead of per-device, I think the global setting is fine, as it serves a specific purpose: don't allow ANY virtio devices without the special handling (like the /390 PV case, SEV, TDX, or Xen PV-guests). Those cases can't sensibly work without the special DMA ops. In case the special DMA ops are just a "nice to have" like for Xen HVM guests, PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS won't be set. And if someone wants a guest only to use grant based virtio devices, the guest kernel can be built with CONFIG_XEN_VIRTIO_FORCE_GRANT (e.g. in case the backends are running in some less privileged environment and thus can't map arbitrary guest memory pages). Juergen Attachment:
OpenPGP_0xB0DE9DD628BF132F.asc Attachment:
OpenPGP_signature
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |