mirror of
https://github.com/xen-project/xen.git
synced 2026-10-28 10:11:27 +01:00
Roger Pau Monne
104591f5dd
When building a PVH dom0 Xen attempts to map all (relevant) MMIO regions into the p2m for dom0 access. However the information Xen has about the host memory map is limited. Xen doesn't have access to any resources described in ACPI dynamic tables, and hence the p2m mappings provided might not be complete. PV doesn't suffer from this issue because a PV dom0 is capable of mapping into it's page-tables any address not explicitly banned in d->iomem_caps. Introduce a new command line options that allows Xen to attempt to fixup the p2m page-faults, by creating p2m identity maps in response to p2m page-faults. This is aimed as a workaround to small ACPI regions Xen doesn't know about. Note that missing large MMIO regions mapped in this way will lead to slowness due to the VM exit processing, plus the mappings will always use small pages. The ultimate aim is to attempt to bring better parity with a classic PV dom0. Note such fixup rely on the CPU doing the access to the unpopulated address. If the access is attempted from a device instead there's no possible way to fixup, as IOMMU page-fault are asynchronous. Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Acked-by: Oleksii Kurochko <oleksii.kurochko@gmail.com> --- Only slightly tested on my local PVH dom0 deployment. --- Changes since v1: - Make the fixup function static. - Print message in case mapping already exists.