Re: [PATCH 00/14 v4] PL011 emulation support in Xen

[Julien Grall <julien.grall@arm.com>]

Hi Bhupinder,

Your patch series is not correctly threaded, every patches came in its 
own thread. Can you please resend a new version correctly threaded?

Cheers,

On 06/06/17 11:01, Bhupinder Thakur wrote:
> PL011 emulation for guests in Xen
> ===================================
> Linaro has published VM System specification for ARM Processors, which
> provides a set of guidelines for both guest OS and hypervisor implementations,
> such that building OS images according to these guidelines guarantees
> that those images can also run on hypervisors compliant with this specification.
>
> One of the spec requirements is that the hypervisor must provide an
> emulated PL011 UART as a serial console which meets the minimum requirements in
> SBSA UART as defined in appendix B of the following
> ARM Server Base Architecture Document:
>
> https://static.docs.arm.com/den0029/a/Server_Base_System_Architecture_v3_1_ARM_DEN_0029A.pdf.
>
> This feature allows the Xen guests to use SBSA compliant pl011 UART as
> as a console.
>
> Note that SBSA pl011 UART is a subset of full featured ARM pl011 UART and
> supports only a subset of registers as mentioned below. It does not support
> rx/tx DMA.
>
> Currently, Xen supports paravirtualized (aka PV console) and an emulated serial
> consoles. This feature will expose an emulated SBSA pl011 UART console to the
> guest, which a user can access using xenconsole.
>
> The device tree passed to the guest VM will contain the pl011 MMIO address
> range and an irq for receiving rx/tx pl011 interrupts. The device tree format
> is specified in Documentation/devicetree/bindings/serial/arm_sbsa_uart.txt.
>
> The Xen hypervisor will expose two types of interfaces to the backend and domU.
>
> The interface exposed to domU will be an emulated pl011 UART by emulating the
> access to the following pl011 registers by the guest.
>
> - Data register (DR)            - RW
> - Raw interrupt status register (RIS)   - RO
> - Masked interrupt status register (MIS)- RO
> - Interrupt Mask (IMSC)         - RW
> - Interrupt Clear (ICR)         - WO
>
> It will also inject the pl011 interrupts to the guest in the following
> conditions:
>
> - incoming data in the rx buffer for the guest
> - there is space in the tx buffer for the guest to write more data
>
> The interface exposed to the backend will be the same PV console interface,
> which minimizes the changes required in xenconsole to support a new pl011 console.
>
> This interface has rx and tx ring buffers and an event channel for
> sending/receiving events from the backend.
>
> So essentially Xen handles the data on behalf of domU and the backend. Any data
> written by domU is captured by Xen and written to the TX (OUT) ring buffer
> and a pl011 event is raised to the backend to read the TX ring buffer.
>
> Similarly on reciving a pl011 event, Xen injects an interrupt to guest to
> indicate there is data available in the RX (IN) ring buffer.
>
> The pl011 UART state is completely captured in the set of registers
> mentioned above and this state is updated everytime there is an event from
> the backend or there is register read/write access from domU.
>
> For example, if domU has masked the rx interrupt in the IMSC register, then Xen
> will not inject an interrupt to guest and will just update the RIS register.
> Once the interrupt is unmasked by guest, the interrupt will be delivered to the
> guest.
>
> Changes summary:
>
> Xen Hypervisor
> ===============
>
> 1. Add emulation code to emulate read/write access to pl011 registers and pl011
>    interrupts:
>     - It emulates DR read/write by reading and writing from/to the IN and
>       OUT ring buffers and raising an event to dom0 when there is data in
>       the OUT ring buffer and injecting an interrupt to the guest when there
>       is data in the IN ring buffer.
>     - Other registers are related to interrupt management and essentially
>       control when interrupts are delivered to the guest.
>
> 2. Add a new domctl API to initialize vpl011 emulation in Xen.
>
> 3. Enable vpl011 emulation for a domain based on a libxl option passed during
>    domain creation.
>
> Toolstack
> ==========
>
> 1. Add a new option "vuart" in the domU configuration file to enable/disable vuart.
>
> 2. Create a SBSA UART DT node in the guest device tree. It uses a fixed
>    vpl011 SPI IRQ number and MMIO address.
>
> 3. Call vpl011 init DOMCTL API to enable vpl011 emulation.
>
> 5. Add a new vuart xenstore node, which contains:
>     - ring-ref
>     - event channel
>     - buffer limit
>     - type
>
> Xenconsoled
> ============
>
> 1. Split the domain structure to support multiple consoles.
>
> 2. Modify different APIs such as buffer_append() etc. to operate on the
>    console structure.
>
> 3. Add support for handling multiple consoles.
>
> 4. Add support for vuart console:
>
> The vpl011 changes available at the following repo:
>
> url: ssh://git@git.linaro.org:/people/bhupinder.thakur/xen.git
> branch: vpl011_v4
>
> There are some TBD items which need to be looked at in the future:
>
> 1. Currently UEFI firmware logs the output to hvc console only. How can
>    UEFI firmware be made aware of pl011 console and how it can use it
>    as a console instead of hvc.
> 2. Linux seems to have hvc console as the default console i.e. if no
>    console is specified then it uses hvc as the console. How can an
>    option be provided in Linux to select either hvc or pl011 as the
>    default console.
>
> 3. ACPI support for pl011 device.
>
> Bhupinder Thakur (14):
>   xen/arm: vpl011: Move vgic register access functions to vreg.h
>   xen/arm: vpl011: Define generic vreg_reg* access functions in vreg.h
>   xen/arm: vpl011: Add pl011 uart emulation in Xen
>   xen/arm: vpl011: Add support for vuart in libxl
>   xen/arm: vpl011: Allocate a new GFN in the toolstack for vuart
>   xen/arm: vpl011: Add a new domctl API to initialize vpl011
>   xen/arm: vpl011: Add a new vuart node in the xenstore
>   xen/arm: vpl011: Modify xenconsole to define and use a new console
>     structure
>   xen/arm: vpl011: Modify xenconsole functions to take console structure
>     as input
>   xen/arm: vpl011: Modify xenconsole to support multiple consoles
>   xen/arm: vpl011: Add support for vuart console in xenconsole
>   xen/arm: vpl011: Add a new vuart console type to xenconsole client
>   xen/arm: vpl011: Add a pl011 uart DT node in the guest device tree
>   xen/arm: vpl011: Update documentation for vuart console support
>
>  config/arm32.mk                      |   1 +
>  config/arm64.mk                      |   1 +
>  docs/man/xl.cfg.pod.5.in             |   9 +
>  docs/misc/console.txt                |  44 ++-
>  tools/console/Makefile               |   4 +-
>  tools/console/client/main.c          |  25 +-
>  tools/console/daemon/io.c            | 544 ++++++++++++++++++++++++-----------
>  tools/libxc/include/xc_dom.h         |   3 +
>  tools/libxc/include/xenctrl.h        |  17 ++
>  tools/libxc/xc_dom_arm.c             |  12 +-
>  tools/libxc/xc_dom_boot.c            |   2 +
>  tools/libxc/xc_domain.c              |  23 ++
>  tools/libxl/libxl.h                  |   6 +
>  tools/libxl/libxl_arch.h             |   7 +
>  tools/libxl/libxl_arm.c              |  71 ++++-
>  tools/libxl/libxl_console.c          |  47 +++
>  tools/libxl/libxl_create.c           |  12 +-
>  tools/libxl/libxl_device.c           |   9 +-
>  tools/libxl/libxl_dom.c              |   8 +-
>  tools/libxl/libxl_internal.h         |   7 +
>  tools/libxl/libxl_types.idl          |   7 +
>  tools/libxl/libxl_types_internal.idl |   1 +
>  tools/libxl/libxl_x86.c              |   8 +
>  tools/xl/Makefile                    |   4 +
>  tools/xl/xl_cmdtable.c               |   4 +
>  tools/xl/xl_console.c                |  11 +-
>  tools/xl/xl_parse.c                  |   8 +
>  xen/arch/arm/Kconfig                 |   5 +
>  xen/arch/arm/Makefile                |   1 +
>  xen/arch/arm/domain.c                |   2 +
>  xen/arch/arm/domctl.c                |  44 ++-
>  xen/arch/arm/vgic-v2.c               |  28 +-
>  xen/arch/arm/vgic-v3.c               |  40 +--
>  xen/arch/arm/vpl011.c                | 418 +++++++++++++++++++++++++++
>  xen/include/asm-arm/domain.h         |   6 +
>  xen/include/asm-arm/pl011-uart.h     |   2 +
>  xen/include/asm-arm/vgic.h           | 111 +------
>  xen/include/asm-arm/vpl011.h         |  74 +++++
>  xen/include/asm-arm/vreg.h           | 109 +++++++
>  xen/include/public/arch-arm.h        |   6 +
>  xen/include/public/domctl.h          |  12 +
>  xen/include/public/io/console.h      |   4 +
>  42 files changed, 1421 insertions(+), 336 deletions(-)
>  create mode 100644 xen/arch/arm/vpl011.c
>  create mode 100644 xen/include/asm-arm/vpl011.h
>

-- 
Julien Grall

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