linux/arch/arm64
Oliver Upton bfbab44568 KVM: arm64: Implement PSCI SYSTEM_SUSPEND
ARM DEN0022D.b 5.19 "SYSTEM_SUSPEND" describes a PSCI call that allows
software to request that a system be placed in the deepest possible
low-power state. Effectively, software can use this to suspend itself to
RAM.

Unfortunately, there really is no good way to implement a system-wide
PSCI call in KVM. Any precondition checks done in the kernel will need
to be repeated by userspace since there is no good way to protect a
critical section that spans an exit to userspace. SYSTEM_RESET and
SYSTEM_OFF are equally plagued by this issue, although no users have
seemingly cared for the relatively long time these calls have been
supported.

The solution is to just make the whole implementation userspace's
problem. Introduce a new system event, KVM_SYSTEM_EVENT_SUSPEND, that
indicates to userspace a calling vCPU has invoked PSCI SYSTEM_SUSPEND.
Additionally, add a CAP to get buy-in from userspace for this new exit
type.

Only advertise the SYSTEM_SUSPEND PSCI call if userspace has opted in.
If a vCPU calls SYSTEM_SUSPEND, punt straight to userspace. Provide
explicit documentation of userspace's responsibilites for the exit and
point to the PSCI specification to describe the actual PSCI call.

Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220504032446.4133305-8-oupton@google.com
2022-05-04 09:28:45 +01:00
..
boot i.MX fixes for 5.18, 2nd round: 2022-04-29 16:23:31 +02:00
configs ARM: DT updates for 5.18 2022-03-23 18:37:22 -07:00
crypto crypto: arm64 - cleanup comments 2022-03-09 15:12:32 +12:00
hyperv arm64: hyperv: Initialize hypervisor on boot 2021-08-04 16:54:36 +00:00
include KVM: arm64: Implement PSCI SYSTEM_SUSPEND 2022-05-04 09:28:45 +01:00
kernel elf: Fix the arm64 MTE ELF segment name and value 2022-04-28 11:37:06 +01:00
kvm KVM: arm64: Implement PSCI SYSTEM_SUSPEND 2022-05-04 09:28:45 +01:00
lib Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2022-03-21 16:02:36 -07:00
mm arm64: fix typos in comments 2022-04-04 10:32:50 +01:00
net kasan, arm64: don't tag executable vmalloc allocations 2022-03-24 19:06:48 -07:00
tools Merge branch 'for-next/spectre-bhb' into for-next/core 2022-03-14 19:08:31 +00:00
xen xen: allow pv-only hypercalls only with CONFIG_XEN_PV 2021-11-02 08:11:01 -05:00
Kbuild kbuild: use more subdir- for visiting subdirectories while cleaning 2021-10-24 13:49:46 +09:00
Kconfig arm64: fix typos in comments 2022-04-14 10:52:53 +01:00
Kconfig.debug arm64: remove TEXT_OFFSET randomization 2020-06-15 13:10:59 +01:00
Kconfig.platforms ARM: DT updates for 5.18 2022-03-23 18:37:22 -07:00
Makefile arm64/xor: use EOR3 instructions when available 2021-12-14 12:14:26 +00:00