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Date: Mon, 18 Jan 2021 14:30:51 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: shuo.a.liu@...el.com, linux-kernel@...r.kernel.org, x86@...nel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"H . Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Yu Wang <yu1.wang@...el.com>,
Reinette Chatre <reinette.chatre@...el.com>,
Zhi Wang <zhi.a.wang@...el.com>, Borislav Petkov <bp@...e.de>,
Dave Hansen <dave.hansen@...el.com>,
Sen Christopherson <sean.j.christopherson@...el.com>,
Dan Williams <dan.j.williams@...el.com>,
Fengwei Yin <fengwei.yin@...el.com>,
Zhenyu Wang <zhenyuw@...ux.intel.com>
Subject: Re: [PATCH v7 01/18] docs: acrn: Introduce ACRN
Hi,
On 1/5/21 11:50 PM, shuo.a.liu@...el.com wrote:
> From: Shuo Liu <shuo.a.liu@...el.com>
>
> Add documentation on the following aspects of ACRN:
>
> 1) A brief introduction on the architecture of ACRN.
> 2) I/O request handling in ACRN.
> 3) CPUID functions of ACRN.
>
> To learn more about ACRN, please go to ACRN project website
> https://projectacrn.org, or the documentation page
> https://projectacrn.github.io/.
>
> Signed-off-by: Shuo Liu <shuo.a.liu@...el.com>
> Reviewed-by: Zhi Wang <zhi.a.wang@...el.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> Reviewed-by: Borislav Petkov <bp@...e.de>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Sen Christopherson <sean.j.christopherson@...el.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Fengwei Yin <fengwei.yin@...el.com>
> Cc: Zhi Wang <zhi.a.wang@...el.com>
> Cc: Zhenyu Wang <zhenyuw@...ux.intel.com>
> Cc: Yu Wang <yu1.wang@...el.com>
> Cc: Reinette Chatre <reinette.chatre@...el.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Randy Dunlap <rdunlap@...radead.org>
> ---
> Documentation/virt/acrn/cpuid.rst | 46 +++++++++++
> Documentation/virt/acrn/index.rst | 12 +++
> Documentation/virt/acrn/introduction.rst | 43 +++++++++++
> Documentation/virt/acrn/io-request.rst | 97 ++++++++++++++++++++++++
> Documentation/virt/index.rst | 1 +
> MAINTAINERS | 7 ++
> 6 files changed, 206 insertions(+)
> create mode 100644 Documentation/virt/acrn/cpuid.rst
> create mode 100644 Documentation/virt/acrn/index.rst
> create mode 100644 Documentation/virt/acrn/introduction.rst
> create mode 100644 Documentation/virt/acrn/io-request.rst
>
> diff --git a/Documentation/virt/acrn/cpuid.rst b/Documentation/virt/acrn/cpuid.rst
> new file mode 100644
> index 000000000000..16727fc412f0
> --- /dev/null
> +++ b/Documentation/virt/acrn/cpuid.rst
> @@ -0,0 +1,46 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +===============
> +ACRN CPUID bits
> +===============
> +
> +A guest VM running on an ACRN hypervisor, can check some of its features using
comma not needed/not wanted.
> +CPUID.
> +
> +ACRN cpuid functions are:
> +
> +function: 0x40000000
> +
> +returns::
> +
> + eax = 0x40000010
> + ebx = 0x4e524341
> + ecx = 0x4e524341
> + edx = 0x4e524341
> +
> +Note that this value in ebx, ecx and edx corresponds to the string
> +"ACRNACRNACRN". The value in eax corresponds to the maximum cpuid function
> +present in this leaf, and will be updated if more functions are added in the
except for the 0x4000000 bit?
> +future.
> +
> +function: define ACRN_CPUID_FEATURES (0x40000001)
> +
> +returns::
> +
> + ebx, ecx, edx
> + eax = an OR'ed group of (1 << flag)
> +
> +where ``flag`` is defined as below:
> +
> +================================= =========== ================================
> +flag value meaning
> +================================= =========== ================================
> +ACRN_FEATURE_PRIVILEGED_VM 0 guest VM is a privileged VM
> +================================= =========== ================================
> +
> +function: 0x40000010
> +
> +returns::
> +
> + ebx, ecx, edx
> + eax = (Virtual) TSC frequency in kHz.
> diff --git a/Documentation/virt/acrn/index.rst b/Documentation/virt/acrn/index.rst
> new file mode 100644
> index 000000000000..b5f793e73df5
> --- /dev/null
> +++ b/Documentation/virt/acrn/index.rst
> @@ -0,0 +1,12 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +===============
> +ACRN Hypervisor
> +===============
> +
> +.. toctree::
> + :maxdepth: 1
> +
> + introduction
> + io-request
> + cpuid
> diff --git a/Documentation/virt/acrn/introduction.rst b/Documentation/virt/acrn/introduction.rst
> new file mode 100644
> index 000000000000..f8d081bc084d
> --- /dev/null
> +++ b/Documentation/virt/acrn/introduction.rst
> @@ -0,0 +1,43 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +ACRN Hypervisor Introduction
> +============================
> +
> +The ACRN Hypervisor is a Type 1 hypervisor, running directly on bare-metal
> +hardware. It has a privileged management VM, called Service VM, to manage User
> +VMs and do I/O emulation.
> +
> +ACRN userspace is an application running in the Service VM that emulates
> +devices for a User VM based on command line configurations. ACRN Hypervisor
> +Service Module (HSM) is a kernel module in the Service VM which provides
> +hypervisor services to the ACRN userspace.
> +
> +Below figure shows the architecture.
> +
> +::
> +
> + Service VM User VM
> + +----------------------------+ | +------------------+
> + | +--------------+ | | | |
> + | |ACRN userspace| | | | |
> + | +--------------+ | | | |
> + |-----------------ioctl------| | | | ...
> + |kernel space +----------+ | | | |
> + | | HSM | | | | Drivers |
> + | +----------+ | | | |
> + +--------------------|-------+ | +------------------+
> + +---------------------hypercall----------------------------------------+
> + | ACRN Hypervisor |
> + +----------------------------------------------------------------------+
> + | Hardware |
> + +----------------------------------------------------------------------+
> +
> +ACRN userspace allocates memory for the User VM, configures and initializes the
> +devices used by the User VM, loads the virtual bootloader, initializes the
> +virtual CPU state and handles I/O request accesses from the User VM. It uses
> +ioctls to communicate with the HSM. HSM implements hypervisor services by
> +interacting with the ACRN Hypervisor via hypercalls. HSM exports a char device
> +interface (/dev/acrn_hsm) to userspace.
> +
> +The ACRN hypervisor is open for contribution from anyone. The source repo is
> +available at https://github.com/projectacrn/acrn-hypervisor.
> diff --git a/Documentation/virt/acrn/io-request.rst b/Documentation/virt/acrn/io-request.rst
> new file mode 100644
> index 000000000000..79022a671ea7
> --- /dev/null
> +++ b/Documentation/virt/acrn/io-request.rst
> @@ -0,0 +1,97 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +I/O request handling
> +====================
> +
> +An I/O request of a User VM, which is constructed by the hypervisor, is
> +distributed by the ACRN Hypervisor Service Module to an I/O client
> +corresponding to the address range of the I/O request. Details of I/O request
> +handling are described in the following sections.
> +
> +1. I/O request
> +--------------
> +
> +For each User VM, there is a shared 4-KByte memory region used for I/O requests
> +communication between the hypervisor and Service VM. An I/O request is a
> +256-byte structure buffer, which is 'struct acrn_io_request', that is filled by
> +an I/O handler of the hypervisor when a trapped I/O access happens in a User
> +VM. ACRN userspace in the Service VM first allocates a 4-KByte page and passes
> +the GPA (Guest Physical Address) of the buffer to the hypervisor. The buffer is
> +used as an array of 16 I/O request slots with each I/O request slot being 256
> +bytes. This array is indexed by vCPU ID.
> +
> +2. I/O clients
> +--------------
> +
> +An I/O client is responsible for handling User VM I/O requests whose accessed
> +GPA falls in a certain range. Multiple I/O clients can be associated with each
> +User VM. There is a special client associated with each User VM, called the
> +default client, that handles all I/O requests that do not fit into the range of
> +any other clients. The ACRN userspace acts as the default client for each User
> +VM.
> +
> +Below illustration shows the relationship between I/O requests shared buffer,
> +I/O requests and I/O clients.
> +
> +::
> +
> + +------------------------------------------------------+
> + | Service VM |
> + |+--------------------------------------------------+ |
> + || +----------------------------------------+ | |
> + || | shared page ACRN userspace | | |
> + || | +-----------------+ +------------+ | | |
> + || +----+->| acrn_io_request |<-+ default | | | |
> + || | | | +-----------------+ | I/O client | | | |
> + || | | | | ... | +------------+ | | |
> + || | | | +-----------------+ | | |
> + || | +-|--------------------------------------+ | |
> + ||---|----|-----------------------------------------| |
> + || | | kernel | |
> + || | | +----------------------+ | |
> + || | | | +-------------+ HSM | | |
> + || | +--------------+ | | | |
> + || | | | I/O clients | | | |
> + || | | | | | | |
> + || | | +-------------+ | | |
> + || | +----------------------+ | |
> + |+---|----------------------------------------------+ |
> + +----|-------------------------------------------------+
> + |
> + +----|-------------------------------------------------+
> + | +-+-----------+ |
> + | | I/O handler | ACRN Hypervisor |
> + | +-------------+ |
> + +------------------------------------------------------+
> +
> +3. I/O request state transition
> +-------------------------------
> +
> +The state transitions of an ACRN I/O request are as follows.
> +
> +::
> +
> + FREE -> PENDING -> PROCESSING -> COMPLETE -> FREE -> ...
> +
> +- FREE: this I/O request slot is empty
> +- PENDING: a valid I/O request is pending in this slot
> +- PROCESSING: the I/O request is being processed
> +- COMPLETE: the I/O request has been processed
> +
> +An I/O request in COMPLETE or FREE state is owned by the hypervisor. HSM and
> +ACRN userspace are in charge of processing the others.
> +
> +4. Processing flow of I/O requests
> +-------------------------------
add 3 more '-' above, please.
> +
> +a. The I/O handler of the hypervisor will fill an I/O request with PENDING
> + state when a trapped I/O access happens in a User VM.
> +b. The hypervisor makes an upcall, which is a notification interrupt, to
> + the Service VM.
> +c. The upcall handler schedules a tasklet to dispatch I/O requests.
> +d. The tasklet looks for the PENDING I/O requests, assigns them to different
> + registered clients based on the address of the I/O accesses, updates
> + their state to PROCESSING, and notifies the corresponding client to handle.
> +e. The notified client handles the assigned I/O requests.
> +f. The HSM updates I/O requests states to COMPLETE and notifies the hypervisor
> + of the completion via hypercalls.
> diff --git a/Documentation/virt/index.rst b/Documentation/virt/index.rst
> index 350f5c869b56..edea7fea95a8 100644
> --- a/Documentation/virt/index.rst
> +++ b/Documentation/virt/index.rst
> @@ -12,6 +12,7 @@ Linux Virtualization Support
> paravirt_ops
> guest-halt-polling
> ne_overview
> + acrn/index
>
> .. only:: html and subproject
thanks for the docs.
--
~Randy
You can't do anything without having to do something else first.
-- Belefant's Law
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