This adds SDEI document, to explain what has been missed from the specification and the pesudo firmware registers used for migration. Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx> --- Documentation/virt/kvm/arm/sdei.rst | 64 +++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) create mode 100644 Documentation/virt/kvm/arm/sdei.rst diff --git a/Documentation/virt/kvm/arm/sdei.rst b/Documentation/virt/kvm/arm/sdei.rst new file mode 100644 index 000000000000..ba1539978b2c --- /dev/null +++ b/Documentation/virt/kvm/arm/sdei.rst @@ -0,0 +1,64 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================================== +SDEI Virtualization Support for ARM64 +===================================== + +ARM specification DEN0054/C defines Software Delegated Exception Interface +(SDEI). It provides a mechanism for registering and servicing system events +from system firmware. The interface is offered by a higher exception level +to a lower exception level, in other words by a secure platform firmware +to hypervisor or hypervisor to OS or both. + +https://developer.arm.com/documentation/den0054/c + +KVM/arm64 implementation follows the specification to support the defined +hypercalls so that the system events can be registered and serviced from +KVM hypervisor to the guest OS. However, some of specified functionalities +are missed by the implementation. + + * The shared event is not supported. It means all supported events are + private. They need to be registered, enabled, disabled, unregistered + and reset from one particular PE (vCPU). + + * The critical priority is not supported. It means all supported events + have normal priority. So there is no preemption between two events + in the critical and normal priorities. One event can be running at + once on one particular PE (vCPU). + + * Interrupt binding event is not supported. It means all supported + events triggered by software. + + * Relative mode for the event handler's address is not supported. + The event handler address is always an absolute address. + +The event handlers, states and context need to be migrated. Several pseudo +firmware registers are added for this. + + * KVM_REG_ARM_SDEI_EVENT_HANDLER_0 + KVM_REG_ARM_SDEI_EVENT_HANDLER_1 + KVM_REG_ARM_SDEI_EVENT_HANDLER_2 + KVM_REG_ARM_SDEI_EVENT_HANDLER_3 + + The event handler's address and argument for events, whose number + are 0, 1, 2 and 3 respectively. Currently, there are only two + supported events, which are Software Signaled Event (0) and Async + PF Event (1). So the first two registers are only used. zeroes are + returned on reading KVM_REG_ARM_SDEI_EVENT_HANDLER_{2, 3}, and the + values written to them are ignored. + + * KVM_REG_ARM_SDEI_EVENT_REGISTERED + KVM_REG_ARM_SDEI_EVENT_ENABLED + KVM_REG_ARM_SDEI_EVENT_RUNNING + KVM_REG_ARM_SDEI_EVENT_PENDING + + They are mapped to the registered, enabled, running and pending + bitmap respectively. + + * KVM_REG_ARM_SDEI_EVENT_CONTEXT + + The interrupted context. + + * KVM_REG_ARM_SDEI_PE_STATE + + Relect the SDEI masked state on the PE (vCPU). -- 2.23.0 _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
