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
..
acrn	docs: acrn: Introduce ACRN	2021-02-09 10:58:18 +01:00
kvm	KVM: arm64: Implement PSCI SYSTEM_SUSPEND	2022-05-04 09:28:45 +01:00
uml	docs: UML: Mention telnetd for port channel	2022-03-11 13:51:03 -07:00
guest-halt-polling.rst	docs: virt: guest-halt-polling.txt convert to ReST	2020-02-12 20:10:08 +01:00
index.rst	docs: acrn: Introduce ACRN	2021-02-09 10:58:18 +01:00
ne_overview.rst	nitro_enclaves: Update documentation for Arm64 support	2021-09-14 11:11:20 +02:00
paravirt_ops.rst