KVM: arm64: Handle PSCI resets before userspace touches vCPU state
The CPU_ON PSCI call takes a payload that KVM uses to configure a destination vCPU to run. This payload is non-architectural state and not exposed through any existing UAPI. Effectively, we have a race between CPU_ON and userspace saving/restoring a guest: if the target vCPU isn't ran again before the VMM saves its state, the requested PC and context ID are lost. When restored, the target vCPU will be runnable and start executing at its old PC. We can avoid this race by making sure the reset payload is serviced before userspace can access a vCPU's state. Fixes: 358b28f0 ("arm/arm64: KVM: Allow a VCPU to fully reset itself") Signed-off-by:Oliver Upton <oupton@google.com> Signed-off-by:
Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20210818202133.1106786-3-oupton@google.com
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