Messages in this thread | | | Date | Wed, 13 Mar 2024 16:04:25 +0100 | Subject | Re: [PATCH RFC] x86/xen: attempt to inflate the memory balloon on PVH | From | Juergen Gross <> |
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On 20.02.24 18:43, Roger Pau Monne wrote: > When running as PVH or HVM Linux will use holes in the memory map as scratch > space to map grants, foreign domain pages and possibly miscellaneous other > stuff. However the usage of such memory map holes for Xen purposes can be > problematic. The request of holesby Xen happen quite early in the kernel boot > process (grant table setup already uses scratch map space), and it's possible > that by then not all devices have reclaimed their MMIO space. It's not > unlikely for chunks of Xen scratch map space to end up using PCI bridge MMIO > window memory, which (as expected) causes quite a lot of issues in the system. > > At least for PVH dom0 we have the possibility of using regions marked as > UNUSABLE in the e820 memory map. Either if the region is UNUSABLE in the > native memory map, or it has been converted into UNUSABLE in order to hide RAM > regions from dom0, the second stage translation page-tables can populate those > areas without issues. > > PV already has this kind of logic, where the balloon driver is inflated at > boot. Re-use the current logic in order to also inflate it when running as > PVH. onvert UNUSABLE regions up to the ratio specified in EXTRA_MEM_RATIO to > RAM, while reserving them using xen_add_extra_mem() (which is also moved so > it's no longer tied to CONFIG_PV). > > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Juergen
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