[PATCH v6 21/21] docs: gunyah: Document Gunyah VM Manager

[Elliot Berman]

On 11/2/2022 6:05 AM, Bagas Sanjaya wrote:
> On Wed, Oct 26, 2022 at 11:58:46AM -0700, Elliot Berman wrote:
>> diff --git a/Documentation/virt/gunyah/vm-manager.rst b/Documentation/virt/gunyah/vm-manager.rst
>> new file mode 100644
>> index 000000000000..c232ba05de7e
>> --- /dev/null
>> +++ b/Documentation/virt/gunyah/vm-manager.rst
>> @@ -0,0 +1,94 @@
>> +.. SPDX-License-Identifier: GPL-2.0
>> +
>> +=======================
>> +Virtual Machine Manager
>> +=======================
>> +
>> +The Gunyah Virtual Machine Manager is a Linux driver to support launching virtual machines.
>> +
>> +Summary
>> +=======
>> +
>> +Gunyah VMM presently supports launching non-proxy scheduled Linux-like virtual machines.
>> +
>> +Sample Userspace VMM
>> +====================
>> +
>> +A sample userspace VMM is included in samples/gunyah/ along with a sample minimal devicetree
>> +that can be used to launch a Linux-like virtual machine under Gunyah. 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.
>> +
>> +Gunyah VM API Descriptions
>> +--------------------------
>> +
>> +GH_VM_SET_USER_MEM_REGION
>> +~~~~~~~~~~~~~~~~~~~~~~~~~
>> +
>> +::
>> +
>> +  struct gh_userspace_memory_region {
>> +	__u32 label;
>> +	__u32 flags;
>> +	__u64 guest_phys_addr;
>> +	__u64 memory_size;
>> +	__u64 userspace_addr;
>> +  };
>> +
>> +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 memory regions with the same label is not allowed.
>> +
>> +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
>> +configured to accept those memory regions at boot-up.
>> +
>> +The guest physical address is used by Linux to check the requested user regions
>> +do not overlap and to help find a corresponding memory region for calls like
>> +GH_VM_SET_DTB_CONFIG.
>> +
>> +To delete a memory region, call GH_VM_SET_USER_MEM_REGION with label set to the
>> +memory region of interest and memory_size set to 0.
>> +
>> +The flags field of gh_userspace_memory_region can set the following bits. All
>> +other bits must be 0 and are reserved for future use. The ioctl will return
>> +-EINVAL if an unsupported bit is detected.
>> +
>> +  - GH_MEM_ALLOW_READ/GH_MEM_ALLOW_WRITE/GH_MEM_ALLOW_EXEC sets read/write/exec permissions
>> +    for the guest, respectively.
>> +
>> +  - GH_MEM_LENT means that the memory will be unmapped from the host and be unaccessible by
>> +    the host while the guest has the region.
>> +
>> +GH_VM_SET_DTB_CONFIG
>> +~~~~~~~~~~~~~~~~~~~~
>> +
>> +::
>> +
>> +  struct gh_vm_dtb_config {
>> +	__u64 gpa;
>> +	__u64 size;
>> +  };
>> +
>> +This ioctl sets the location of the VM's devicetree blob and is used by Gunyah
>> +Resource Manager to allocate resources.
>> +
>> +GH_VM_START
>> +~~~~~~~~~~~
>> +
>> +This ioctl starts the virtual machine.
> 
> I think the wording can be better:
> 
> ---- >8 ----
> 
> diff --git a/Documentation/virt/gunyah/vm-manager.rst b/Documentation/virt/gunyah/vm-manager.rst
> index c232ba05de7e96..772fd970b91d7e 100644
> --- a/Documentation/virt/gunyah/vm-manager.rst
> +++ b/Documentation/virt/gunyah/vm-manager.rst
> @@ -4,18 +4,15 @@
>   Virtual Machine Manager
>   =======================
>   
> -The Gunyah Virtual Machine Manager is a Linux driver to support launching virtual machines.
> -
> -Summary
> -=======
> -
> -Gunyah VMM presently supports launching non-proxy scheduled Linux-like virtual machines.
> +The Gunyah Virtual Machine Manager is a Linux driver for launching virtual
> +machines using Gunyah. It presently supports launching non-proxy scheduled
> +Linux-like virtual machines.
>   
>   Sample Userspace VMM
>   ====================
>   
> -A sample userspace VMM is included in samples/gunyah/ along with a sample minimal devicetree
> -that can be used to launch a Linux-like virtual machine under Gunyah. To build this sample, enable
> +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
> @@ -23,7 +20,8 @@ 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.
> +To create a VM, use the GH_CREATE_VM ioctl. A successful call will return a
> +"Gunyah VM" file descriptor.
>   
>   /dev/gunyah API Descriptions
>   ----------------------------
> @@ -51,29 +49,28 @@ 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 memory regions with the same label is not allowed.
> +attempting to create two regions with the same label is not allowed.
>   
>   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
> -configured to accept those memory regions at boot-up.
> +Thus, memory regions should be provided before starting the VM and the VM must
> +be configured to accept these at boot-up.
>   
> -The guest physical address is used by Linux to check the requested user regions
> -do not overlap and to help find a corresponding memory region for calls like
> -GH_VM_SET_DTB_CONFIG.
> +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.
>   
>   To delete a memory region, call GH_VM_SET_USER_MEM_REGION with label set to the
> -memory region of interest and memory_size set to 0.
> +desired region and memory_size set to 0.
>   
> -The flags field of gh_userspace_memory_region can set the following bits. All
> +The flags field of gh_userspace_memory_region accepts the following bits. All
>   other bits must be 0 and are reserved for future use. The ioctl will return
>   -EINVAL if an unsupported bit is detected.
>   
> -  - GH_MEM_ALLOW_READ/GH_MEM_ALLOW_WRITE/GH_MEM_ALLOW_EXEC sets read/write/exec permissions
> -    for the guest, respectively.
> -
> -  - GH_MEM_LENT means that the memory will be unmapped from the host and be unaccessible by
> -    the host while the guest has the region.
> +  - GH_MEM_ALLOW_READ/GH_MEM_ALLOW_WRITE/GH_MEM_ALLOW_EXEC sets read/write/exec
> +    permissions for the guest, respectively.
> +  - GH_MEM_LENT means that the memory will be unmapped from the host and be
> +    unaccessible by the host while the guest has the region.

One side question -- before, you asked that I add newline between the 
list entries. Here, you've removed them. When do I need the extra 
newline vs not?

https://lore.kernel.org/all/YzUUaIx+azyzFDNX@debian.me/

>   
>   GH_VM_SET_DTB_CONFIG
>   ~~~~~~~~~~~~~~~~~~~~
> @@ -91,4 +88,4 @@ Resource Manager to allocate resources.
>   GH_VM_START
>   ~~~~~~~~~~~
>   
> -This ioctl starts the virtual machine.
> +This ioctl starts the VM.
> 
> Thanks.
> 

Thanks for reviewing and providing all the suggestions. I've applied all 
of them.