Re: [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@xxxxxxxxx/

>   
>   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.