mbox series

[V6,0/2] Add handling of extended regions (safe ranges) on Arm (Was "xen/memory: Introduce a hypercall to provide unallocated space")

Message ID 1633974539-7380-1-git-send-email-olekstysh@gmail.com (mailing list archive)
Headers show
Series Add handling of extended regions (safe ranges) on Arm (Was "xen/memory: Introduce a hypercall to provide unallocated space") | expand

Message

Oleksandr Tyshchenko Oct. 11, 2021, 5:48 p.m. UTC 
From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

You can find an initial discussion at [1]-[6].

The extended region (safe range) is a region of guest physical address space
which is unused and could be safely used to create grant/foreign mappings instead
of wasting real RAM pages from the domain memory for establishing these mappings.

The extended regions are chosen at the domain creation time and advertised
to it via "reg" property under hypervisor node in the guest device-tree
(the indexes for extended regions are 1...N).
No device tree bindings update is needed, guest infers the presense of extended
regions from the number of regions in "reg" property.
New compatible/property will be needed (but only after this patch [7] or alternative
goes in) to indicate that "region 0 is safe to use". Until this patch is merged it is
not safe to use extended regions for the grant table space.

The extended regions are calculated differently for direct mapped Dom0 (with and without
IOMMU) and non-direct mapped DomUs.

Please note the following limitations:
- The extended region feature is only supported for 64-bit domain currently.
- The ACPI case is not covered.

Please note that support for Dom0 was already committed, so these patches are remaining DomU bits.

Xen patch series is also available at [8]. The corresponding Linux patch series is at [9]
for now (last 4 patches).

Tested on Renesas Salvator-X board + H3 ES3.0 SoC (Arm64) with updated virtio-disk backend [10]
running in Dom0 (256MB RAM) and DomD (2GB RAM). In both cases the backend pre-maps DomU memory
which is 3GB. All foreign memory gets mapped into extended regions (so the amount of RAM in
the backend domain is not reduced). No issues were observed.

[1] https://lore.kernel.org/xen-devel/1627489110-25633-1-git-send-email-olekstysh@gmail.com/
[2] https://lore.kernel.org/xen-devel/1631034578-12598-1-git-send-email-olekstysh@gmail.com/
[3] https://lore.kernel.org/xen-devel/1631297924-8658-1-git-send-email-olekstysh@gmail.com/
[4] https://lore.kernel.org/xen-devel/1632437334-12015-1-git-send-email-olekstysh@gmail.com/
[5] https://lore.kernel.org/xen-devel/1632955927-27911-1-git-send-email-olekstysh@gmail.com/
[6] https://lore.kernel.org/xen-devel/1633519346-3686-1-git-send-email-olekstysh@gmail.com/
[7] https://lore.kernel.org/xen-devel/1632425551-18910-1-git-send-email-olekstysh@gmail.com/
[8] https://github.com/otyshchenko1/xen/commits/map_opt_ml7
[9] https://github.com/otyshchenko1/linux/commits/map_opt_ml4
[10] https://github.com/otyshchenko1/virtio-disk/commits/map_opt_next

Oleksandr Tyshchenko (2):
  xen/arm: Introduce gpaddr_bits field to struct
    xen_domctl_getdomaininfo
  libxl/arm: Add handling of extended regions for DomU

 tools/include/libxl.h            |  8 +++++
 tools/include/xenctrl.h          |  1 +
 tools/libs/ctrl/xc_domain.c      |  1 +
 tools/libs/light/libxl_arm.c     | 76 +++++++++++++++++++++++++++++++++++++---
 tools/libs/light/libxl_domain.c  |  1 +
 tools/libs/light/libxl_types.idl |  1 +
 xen/arch/arm/domctl.c            |  2 ++
 xen/arch/x86/domctl.c            |  1 +
 xen/include/public/arch-arm.h    |  2 ++
 xen/include/public/domctl.h      |  3 +-
 10 files changed, 90 insertions(+), 6 deletions(-)