[PATCH v6 0/4] Enable guest suspend/resume support on ARM via vPSCI

[Mykola Kvach <xakep.amatop@xxxxxxxxx>]

From: Mykola Kvach <mykola_kvach@xxxxxxxx>

This patch series introduces the initial support for guest suspend
and resume on ARM platforms using the PSCI SYSTEM_SUSPEND interface. The main
goal is to allow ARM guests to request suspension using PSCI and be resumed
by the control domain (e.g., via "xl resume").

### Background

The PSCI SYSTEM_SUSPEND call is part of the PSCI v1.0+ specification and is
used by guests to enter the deepest possible power state. On Xen/ARM, we
emulate this interface in the virtual PSCI (vPSCI) layer for guests.

This series includes:

1. A new vPSCI implementation of the PSCI SYSTEM_SUSPEND function for guests
2. Documentation updates to SUPPORT.md to reflect PSCI and vPSCI support status
3. Enabling "xl resume" command compilation for ARM, which was previously 
disabled

### Usage

For Linux-based guests:
  - Suspend can be triggered using: "echo mem > /sys/power/state" or "systemctl 
suspend"
  - Resume can be performed from control domain using: "xl resume <domain>"

For more information, refer to the official Linux kernel documentation on power 
management.

Note that currently, SYSTEM_SUSPEND is supported only for guest domains (not for
the hardware domain).
---

TODO: enable "xl suspend" for ARM
---
Previous versions of this patch series:
  V1: https://lists.xenproject.org/archives/html/xen-devel/2018-11/msg01093.html
  V2: https://marc.info/?l=xen-devel&m=166514782207736&w=2
  V3: https://lists.xenproject.org/archives/html/xen-devel/2025-03/msg00168.html


This is the first part of previous patch series and originally consist only
with necessary changes needed for guest domain suspend.

Main changes in V6:
- Skip execution of ctxt_switch_from for VCPUs in paused domains.
- Implement domain_resume_nopause
- Add a helper to determine if a VCPU is in suspended domain.
- Ignore upper 32 bits of arguments for 64-bit domains calling SMC32 
SYSTEM_SUSPEND.
- Macro renamed from LIBXL_HAVE_NO_SUSPEND_RESUME to LIBXL_HAVE_NO_SUSPEND for 
clarity.
- Documentation now focuses only on the SYSTEM_SUSPEND function, with improved 
wording and structure.
- Changelog and commit messages refined for clarity and to remove redundant 
explanations.

Main change in V5:
  - Reverted the logic related to suspending domains. Instead of the standby
    mode introduced in v4, domains now resume execution at the point provided
    during suspend

The rest of the minor changes are described in the changelog of each commit.

Mykola Kvach (4):
  xen/arm: Implement PSCI SYSTEM_SUSPEND call for guests
  tools/xl: Allow compilation of 'xl resume' command on Arm
  SUPPORT.md: Document PSCI SYSTEM_SUSPEND support for guests
  CHANGELOG: Document guest suspend/resume to RAM support on Arm

 CHANGELOG.md                          |  2 +
 SUPPORT.md                            |  5 +-
 tools/include/libxl.h                 |  5 +-
 tools/xl/xl.h                         | 10 +--
 tools/xl/xl_cmdtable.c                |  8 +--
 tools/xl/xl_migrate.c                 |  4 +-
 tools/xl/xl_saverestore.c             |  4 +-
 tools/xl/xl_vmcontrol.c               | 14 ++---
 xen/arch/arm/domain.c                 |  4 ++
 xen/arch/arm/include/asm/perfc_defn.h |  1 +
 xen/arch/arm/include/asm/psci.h       |  2 +
 xen/arch/arm/include/asm/vpsci.h      |  2 +-
 xen/arch/arm/vpsci.c                  | 90 +++++++++++++++++++++++----
 xen/common/domain.c                   | 30 ++++++---
 xen/include/xen/sched.h               |  2 +
 15 files changed, 137 insertions(+), 46 deletions(-)

-- 
2.48.1