Re: [PATCH v13 15/24] docs: gunyah: Document Gunyah VM Manager

On 5/9/23 3:47 PM, Elliot Berman wrote:

Document the ioctls and usage of Gunyah VM Manager driver.

Signed-off-by: Elliot Berman <redacted>

This patch does not apply, because at this point in the
series, "Documentation/virt/gunyah/index.rst" does not
exist.  I'm going to ignore that.

I have some suggestions, but this generally looks good.
I'll wait to see v14 with the full "index.rst" before I
give my Reviewed-by.

					-Alex

Does everyone know what "non-proxy-scheduled virtual machines" are?

+Except for some basic information about the location of initial binaries,
+most of the configuration about a Gunyah virtual machine is described in the
+VM's devicetree. The devicetree is generated by userspace. Interacting with the
+virtual machine is still done via the kernel and VM configuration requires some
+of the corresponding functionality to be set up in the kernel. For instance,
+sharing userspace memory with a VM is done via the `GH_VM_SET_USER_MEM_REGION`_
+ioctl. The VM itself is configured to use the memory region via the
+devicetree.

Without looking at the code, I'm a little unsure what that last
sentence reallly means.

+
+Sample Userspace VMM
+====================
+
+A sample userspace VMM is included in samples/gunyah/ along with a minimal
+devicetree that can be used to launch a VM. To build this sample, enable
+CONFIG_SAMPLE_GUNYAH.
+
+IOCTLs and userspace VMM flows
+==============================
+
+The kernel exposes a char device interface at /dev/gunyah.
+
+To create a VM, use the `GH_CREATE_VM`_ ioctl. A successful call will return a
+"Gunyah VM" file descriptor.
+
+/dev/gunyah API Descriptions
+----------------------------
+
+GH_CREATE_VM
+~~~~~~~~~~~~
+
+Creates a Gunyah VM. The argument is reserved for future use and must be 0.

Maybe mention it returns a file descriptor representing the created VM?

+
+Gunyah VM API Descriptions
+--------------------------
+
+GH_VM_SET_USER_MEM_REGION
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This ioctl allows the user to create or delete a memory parcel for a guest
+virtual machine. Each memory region is uniquely identified by a label;
+attempting to create two regions with the same label is not allowed. Labels are
+unique per virtual machine.
+
+While VMM is guest-agnostic and allows runtime addition of memory regions,
+Linux guest virtual machines do not support accepting memory regions at runtime.
+Thus, memory regions should be provided before starting the VM and the VM must

Thus, for Linux guests, memory regions must be provided...

+be configured to accept these at boot-up.
+
+The guest physical address is used by Linux kernel to check that the requested
+user regions do not overlap and to help find the corresponding memory region
+for calls like `GH_VM_SET_DTB_CONFIG`_. It must be page aligned.
+
+To add a memory region, call `GH_VM_SET_USER_MEM_REGION`_ with fields set as
+described above.
+
+.. kernel-doc:: include/uapi/linux/gunyah.h
+   :identifiers: gh_userspace_memory_region gh_mem_flags
+
+GH_VM_SET_DTB_CONFIG
+~~~~~~~~~~~~~~~~~~~~
+
+This ioctl sets the location of the VM's devicetree blob and is used by Gunyah
+Resource Manager to allocate resources. The guest physical memory should be part

s/should/must/		/* ? */

+of the primary memory parcel provided to the VM prior to GH_VM_START.

Is it possible to provide multiple memory parcels?  If so, is the
"primary" memory parcel the first?

+
+.. kernel-doc:: include/uapi/linux/gunyah.h
+   :identifiers: gh_vm_dtb_config
+
+GH_VM_START
+~~~~~~~~~~~
+
+This ioctl starts the VM.

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