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Subject: Re: [PATCH v9 01/18] docs: acrn: Introduce ACRN
To:     shuo.a.liu@intel.com, linux-kernel@vger.kernel.org, x86@kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Yu Wang <yu1.wang@intel.com>,
        Reinette Chatre <reinette.chatre@intel.com>,
        Zhi Wang <zhi.a.wang@intel.com>, Borislav Petkov <bp@suse.de>,
        Dave Hansen <dave.hansen@intel.com>,
        Sen Christopherson <sean.j.christopherson@intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Fengwei Yin <fengwei.yin@intel.com>,
        Zhenyu Wang <zhenyuw@linux.intel.com>
References: <20210207031040.49576-1-shuo.a.liu@intel.com>
 <20210207031040.49576-2-shuo.a.liu@intel.com>
From:   Randy Dunlap <rdunlap@infradead.org>
Message-ID: <6ae2679c-e172-a955-9df5-2b54b79dd854@infradead.org>
Date:   Mon, 8 Feb 2021 11:48:07 -0800
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Hi--

On 2/6/21 7:10 PM, shuo.a.liu@intel.com wrote:
> From: Shuo Liu <shuo.a.liu@intel.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.

> ---

> diff --git a/Documentation/virt/acrn/io-request.rst b/Documentation/virt/acrn/io-request.rst
> new file mode 100644
> index 000000000000..6cc3ea0fa1f5
> --- /dev/null
> +++ b/Documentation/virt/acrn/io-request.rst
> @@ -0,0 +1,97 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +I/O request handling
> +====================
> +
...
> +
> +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.

Does this mean that ACRN has a limit of 16 vCPUs ?

thanks.
-- 
~Randy