Hi Randy,
On Mon 8.Feb'21 at 11:48:07 -0800, Randy Dunlap wrote:
On 2/6/21 7:10 PM, shuo.a....@intel.com wrote:
From: Shuo Liu <shuo.a....@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
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+.. 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 ?
Yes. Now it is a limitation.
Thanks
shuo
