Messages in this thread | | | Date | Tue, 28 Feb 2023 16:00:48 -0800 | Subject | Re: [PATCH v10 01/26] docs: gunyah: Introduce Gunyah Hypervisor | From | Elliot Berman <> |
| |
On 2/23/2023 3:41 PM, Alex Elder wrote: > On 2/14/23 3:12 PM, Elliot Berman wrote: >> Gunyah is an open-source Type-1 hypervisor developed by Qualcomm. It >> does not depend on any lower-privileged OS/kernel code for its core >> functionality. This increases its security and can support a smaller >> trusted computing based when compared to Type-2 hypervisors. >> >> Add documentation describing the Gunyah hypervisor and the main >> components of the Gunyah hypervisor which are of interest to Linux >> virtualization development. >> >> Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com> >> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com> >> --- >> Documentation/virt/gunyah/index.rst | 113 ++++++++++++++++++++ >> Documentation/virt/gunyah/message-queue.rst | 61 +++++++++++ >> Documentation/virt/index.rst | 1 + >> 3 files changed, 175 insertions(+) >> create mode 100644 Documentation/virt/gunyah/index.rst >> create mode 100644 Documentation/virt/gunyah/message-queue.rst >> >> diff --git a/Documentation/virt/gunyah/index.rst >> b/Documentation/virt/gunyah/index.rst >> new file mode 100644 >> index 000000000000..45adbbc311db >> --- /dev/null >> +++ b/Documentation/virt/gunyah/index.rst >> @@ -0,0 +1,113 @@ >> +.. SPDX-License-Identifier: GPL-2.0 >> + >> +================= >> +Gunyah Hypervisor >> +================= >> + >> +.. toctree:: >> + :maxdepth: 1 >> + >> + message-queue >> + >> +Gunyah is a Type-1 hypervisor which is independent of any OS kernel, >> and runs in >> +a higher CPU privilege level. It does not depend on any >> lower-privileged operating system >> +for its core functionality. This increases its security and can >> support a much smaller >> +trusted computing base than a Type-2 hypervisor. >> + >> +Gunyah is an open source hypervisor. The source repo is available at >> +https://github.com/quic/gunyah-hypervisor. >> + >> +Gunyah provides these following features. >> + >> +- Scheduling: >> + >> + A scheduler for virtual CPUs (vCPUs) on physical CPUs enables >> time-sharing >> + of the CPUs. Gunyah supports two models of scheduling: >> + >> + 1. "Behind the back" scheduling in which Gunyah hypervisor >> schedules vCPUS on its own. >> + 2. "Proxy" scheduling in which a delegated VM can donate part of >> one of its vCPU slice >> + to another VM's vCPU via a hypercall. >> + >> +- Memory Management: >> + >> + APIs handling memory, abstracted as objects, limiting direct use of >> physical >> + addresses. Memory ownership and usage tracking of all memory under >> its control. >> + Memory partitioning between VMs is a fundamental security feature. >> + >> +- Interrupt Virtualization: >> + >> + Uses CPU hardware interrupt virtualization capabilities. Interrupts >> are handled >> + in the hypervisor and routed to the assigned VM. >> + >> +- Inter-VM Communication: >> + >> + There are several different mechanisms provided for communicating >> between VMs. >> + >> +- Virtual platform: >> + >> + Architectural devices such as interrupt controllers and CPU timers >> are directly provided >> + by the hypervisor as well as core virtual platform devices and >> system APIs such as ARM PSCI. >> + >> +- Device Virtualization: >> + >> + Para-virtualization of devices is supported using inter-VM >> communication. >> + >> +Architectures supported >> +======================= >> +AArch64 with a GIC >> + >> +Resources and Capabilities >> +========================== >> + >> +Some services or resources provided by the Gunyah hypervisor are >> described to a virtual machine by >> +capability IDs. For instance, inter-VM communication is performed >> with doorbells and message queues. >> +Gunyah allows access to manipulate that doorbell via the capability >> ID. These resources are >> +described in Linux as a struct gunyah_resource. >> + >> +High level management of these resources is performed by the resource >> manager VM. RM informs a >> +guest VM about resources it can access through either the device tree >> or via guest-initiated RPC. >> + >> +For each virtual machine, Gunyah maintains a table of resources which >> can be accessed by that VM. >> +An entry in this table is called a "capability" and VMs can only >> access resources via this >> +capability table. Hence, virtual Gunyah resources are referenced by a >> "capability IDs" and not >> +"resource IDs". If 2 VMs have access to the same resource, they might >> not be using the same >> +capability ID to access that resource since the capability tables are >> independent per VM. >> + >> +Resource Manager >> +================ >> + >> +The resource manager (RM) is a privileged application VM supporting >> the Gunyah Hypervisor. >> +It provides policy enforcement aspects of the virtualization system. >> The resource manager can >> +be treated as an extension of the Hypervisor but is separated to its >> own partition to ensure >> +that the hypervisor layer itself remains small and secure and to >> maintain a separation of policy >> +and mechanism in the platform. RM runs at arm64 NS-EL1 similar to >> other virtual machines. >> + >> +Communication with the resource manager from each guest VM happens >> with message-queue.rst. Details >> +about the specific messages can be found in >> drivers/virt/gunyah/rsc_mgr.c >> + >> +:: >> + >> + +-------+ +--------+ +--------+ >> + | RM | | VM_A | | VM_B | >> + +-.-.-.-+ +---.----+ +---.----+ >> + | | | | >> + +-.-.-----------.------------.----+ >> + | | \==========/ | | >> + | \========================/ | >> + | Gunyah | >> + +---------------------------------+ >> + >> +The source for the resource manager is available at >> https://github.com/quic/gunyah-resource-manager. >> + >> +The resource manager provides the following features: >> + >> +- VM lifecycle management: allocating a VM, starting VMs, destruction >> of VMs >> +- VM access control policy, including memory sharing and lending >> +- Interrupt routing configuration >> +- Forwarding of system-level events (e.g. VM shutdown) to owner VM >> + >> +When booting a virtual machine which uses a devicetree such as Linux, >> resource manager overlays a >> +/hypervisor node. This node can let Linux know it is running as a >> Gunyah guest VM, >> +how to communicate with resource manager, and basic description and >> capabilities of >> +this VM. See >> Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml for >> a description >> +of this node. >> diff --git a/Documentation/virt/gunyah/message-queue.rst >> b/Documentation/virt/gunyah/message-queue.rst >> new file mode 100644 >> index 000000000000..0667b3eb1ff9 >> --- /dev/null >> +++ b/Documentation/virt/gunyah/message-queue.rst >> @@ -0,0 +1,61 @@ >> +.. SPDX-License-Identifier: GPL-2.0 >> + >> +Message Queues >> +============== >> +Message queue is a simple low-capacity IPC channel between two VMs. >> It is >> +intended for sending small control and configuration messages. Each >> message >> +queue is unidirectional, so a full-duplex IPC channel requires a pair >> of queues. >> + >> +Messages can be up to 240 bytes in length. Longer messages require a >> further >> +protocol on top of the message queue messages themselves. For >> instance, communication >> +with the resource manager adds a header field for sending longer >> messages via multiple >> +message fragments. >> + >> +The diagram below shows how message queue works. A typical >> configuration involves >> +2 message queues. Message queue 1 allows VM_A to send messages to >> VM_B. Message >> +queue 2 allows VM_B to send messages to VM_A. >> + >> +1. VM_A sends a message of up to 240 bytes in length. It raises a >> hypercall > > Can you clarify that the message being sent is in the VM's *own* > memory/ Maybe this is clear, but the message doesn't have to (for > example) be located in shared memory. The original message is > copied into message queue buffers in order to be transferred. > >> + with the message to inform the hypervisor to add the message to >> + message queue 1's queue. >> + >> +2. Gunyah raises the corresponding interrupt for VM_B (Rx vIRQ) when >> any of >> + these happens: >> + >> + a. gh_msgq_send has PUSH flag. Queue is immediately flushed. This >> is the typical case. > > Below you use gh_msgq_send() (with parentheses). I prefer that, > but whatever you do, do it consistently. > >> + b. Explicility with gh_msgq_push command from VM_A. >> + c. Message queue has reached a threshold depth. >> + >> +3. VM_B calls gh_msgq_recv and Gunyah copies message to requested >> buffer. >> + >> +4. Gunyah buffers messages in the queue. If the queue became full >> when VM_A added a message, >> + the return values for gh_msgq_send() include a flag that indicates >> the queue is full. >> + Once VM_B receives the message and, thus, there is space in the >> queue, Gunyah >> + will raise the Tx vIRQ on VM_A to indicate it can continue sending >> messages. >> + >> +For VM_B to send a message to VM_A, the process is identical, except >> that hypercalls >> +reference message queue 2's capability ID. Each message queue has its >> own independent >> +vIRQ: two TX message queues will have two vIRQs (and two capability >> IDs). > > Can a sender determine when a message has been delivered?
Sender cannot determine when the receiving VM has processed the message.
> Does the TX vIRQ indicate only that the messaging system > has processed the message (taken it and queued it), but > says nothing about it being delivered/accepted/received?
That's the correct interpretation.
Thanks, Elliot
| |