hw/arm: introduce xenpvh machine

Add a new machine xenpvh which creates a IOREQ server to register/connect with
Xen Hypervisor.

Optional: When CONFIG_TPM is enabled, it also creates a tpm-tis-device, adds a
TPM emulator and connects to swtpm running on host machine via chardev socket
and support TPM functionalities for a guest domain.

Extra command line for aarch64 xenpvh QEMU to connect to swtpm:
    -chardev socket,id=chrtpm,path=/tmp/myvtpm2/swtpm-sock \
    -tpmdev emulator,id=tpm0,chardev=chrtpm \
    -machine tpm-base-addr=0x0c000000 \

swtpm implements a TPM software emulator(TPM 1.2 & TPM 2) built on libtpms and
provides access to TPM functionality over socket, chardev and CUSE interface.
Github repo: https://github.com/stefanberger/swtpm
Example for starting swtpm on host machine:
    mkdir /tmp/vtpm2
    swtpm socket --tpmstate dir=/tmp/vtpm2 \
    --ctrl type=unixio,path=/tmp/vtpm2/swtpm-sock &

Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

docs/system/arm/xenpvh.rst

@@ -0,0 +1,34 @@
+XENPVH (``xenpvh``)
+=========================================
+This machine creates a IOREQ server to register/connect with Xen Hypervisor.
+
+When TPM is enabled, this machine also creates a tpm-tis-device at a user input
+tpm base address, adds a TPM emulator and connects to a swtpm application
+running on host machine via chardev socket. This enables xenpvh to support TPM
+functionalities for a guest domain.
+
+More information about TPM use and installing swtpm linux application can be
+found at: docs/specs/tpm.rst.
+
+Example for starting swtpm on host machine:
+.. code-block:: console
+
+    mkdir /tmp/vtpm2
+    swtpm socket --tpmstate dir=/tmp/vtpm2 \
+    --ctrl type=unixio,path=/tmp/vtpm2/swtpm-sock &
+
+Sample QEMU xenpvh commands for running and connecting with Xen:
+.. code-block:: console
+
+    qemu-system-aarch64 -xen-domid 1 \
+    -chardev socket,id=libxl-cmd,path=qmp-libxl-1,server=on,wait=off \
+    -mon chardev=libxl-cmd,mode=control \
+    -chardev socket,id=libxenstat-cmd,path=qmp-libxenstat-1,server=on,wait=off \
+    -mon chardev=libxenstat-cmd,mode=control \
+    -xen-attach -name guest0 -vnc none -display none -nographic \
+    -machine xenpvh -m 1301 \
+    -chardev socket,id=chrtpm,path=tmp/vtpm2/swtpm-sock \
+    -tpmdev emulator,id=tpm0,chardev=chrtpm -machine tpm-base-addr=0x0C000000
+
+In above QEMU command, last two lines are for connecting xenpvh QEMU to swtpm
+via chardev socket.

docs/system/target-arm.rst

@@ -107,6 +107,7 @@ undocumented; you can get a complete list by running
    arm/stm32
    arm/virt
    arm/xlnx-versal-virt
+   arm/xenpvh
 
 Emulated CPU architecture support
 =================================