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| author | Roger Pau Monne <roger.pau@citrix.com> | 2020-09-01 11:33:26 +0300 |
|---|---|---|
| committer | Juergen Gross <jgross@suse.com> | 2020-09-04 11:00:01 +0300 |
| commit | 9e2369c06c8a181478039258a4598c1ddd2cadfa (patch) | |
| tree | 4a5834c69de9fb3864acd24e078dd765fb69b21c /drivers/xen/Kconfig | |
| parent | 4533d3aed857c558d6aabd00d0cb04100c5a2258 (diff) | |
| download | linux-9e2369c06c8a181478039258a4598c1ddd2cadfa.tar.xz | |
xen: add helpers to allocate unpopulated memory
To be used in order to create foreign mappings. This is based on the
ZONE_DEVICE facility which is used by persistent memory devices in
order to create struct pages and kernel virtual mappings for the IOMEM
areas of such devices. Note that on kernels without support for
ZONE_DEVICE Xen will fallback to use ballooned pages in order to
create foreign mappings.
The newly added helpers use the same parameters as the existing
{alloc/free}_xenballooned_pages functions, which allows for in-place
replacement of the callers. Once a memory region has been added to be
used as scratch mapping space it will no longer be released, and pages
returned are kept in a linked list. This allows to have a buffer of
pages and prevents resorting to frequent additions and removals of
regions.
If enabled (because ZONE_DEVICE is supported) the usage of the new
functionality untangles Xen balloon and RAM hotplug from the usage of
unpopulated physical memory ranges to map foreign pages, which is the
correct thing to do in order to avoid mappings of foreign pages depend
on memory hotplug.
Note the driver is currently not enabled on Arm platforms because it
would interfere with the identity mapping required on some platforms.
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20200901083326.21264-4-roger.pau@citrix.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'drivers/xen/Kconfig')
| -rw-r--r-- | drivers/xen/Kconfig | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig index 46e7fd099904..0ab54df82520 100644 --- a/drivers/xen/Kconfig +++ b/drivers/xen/Kconfig @@ -324,4 +324,14 @@ config XEN_HAVE_VPMU config XEN_FRONT_PGDIR_SHBUF tristate +config XEN_UNPOPULATED_ALLOC + bool "Use unpopulated memory ranges for guest mappings" + depends on X86 && ZONE_DEVICE + default XEN_BACKEND || XEN_GNTDEV || XEN_DOM0 + help + Use unpopulated memory ranges in order to create mappings for guest + memory regions, including grant maps and foreign pages. This avoids + having to balloon out RAM regions in order to obtain physical memory + space to create such mappings. + endmenu |