Re: [Qemu-devel] [RFC PATCH 00/34] Multi Architecture System Emulation

[Peter Crosthwaite]

On Sun, May 10, 2015 at 11:29 PM, Peter Crosthwaite
<address@hidden> wrote:
> Hi All,
>
> This is target-multi, a system-mode build that can support multiple
> cpu-types. Patches 1-3 are the main infrastructure. The hard part
> is the per-target changes needed to get each arch into an includable
> state.
>
> Two architectures are initially converted. Microblaze and ARM. Step
> by step conversion in done for each. A microblaze is added to
> Xilinx Zynq platform as a test case. This will be elaborted more in
> future spins. This use case is valid, as Microblazes can be added (any
> number of them!) in Zynq FPGA programmable logic configuration.
>
> The hardest part is what to do about bootloading. Currently each arch
> has it's own architecture specific bootloading which may assume a
> single architecture. I have applied some hacks to at least get this
> RFC testable using a -kernel -firmware split but going forward being
> able to associate an elf/image with a cpu explictitly needs to be
> solved.
>
> For the implementation of this series, the trickiest part is cpu.h
> inclusion management. There are now more than one cpu.h's and different
> parts of the tree need a different include scheme. target-multi defines
> it's own cpu.h which is bare minimum defs as needed by core code only.
> target-foo/cpu.h are mostly the same but refactored to reuse common
> code (with target-multi/cpu-head.h). Inclusion scheme goes something like
> this (for the multi-arch build):
>
> 1: All obj-y modules include target-multi/cpu.h
> 2: Core code includes no other cpu.h's
> 3: target-foo/ implementation code includes target-foo/cpu.h
> 4: System level code (e.g. mach models) can use multiple target-foo/cpu.h's
>
> Point 4 means that cpu.h's needs to be refactored to be able to include one
> after the other. The interrupts for ARM and MB needed to be renamed to avoid
> namespace collision. A few other defs needed multiple include guards, and
> a few defs which where only for user mode are compiled out or relocated. No
> attempt at support for multi-arch linux-user mode (if that even makes sense?).
>
> The env as handle by common code now needs to architecture-agnostic. The
> MB and ARM envs are refactored to have CPU_COMMON as the first field(s)
> allowing QOM-style pointer casts to/from a generic env which contains only
> CPU_COMMON. Might need to lock down some struct packing for that but it
> works for me so far.
>
> The helper function namespace is going to be tricky. I haven't tackled the
> problem just yet, but looking for ideas on how we can avoid prefacing all
> helpers with arch prefixes to avoid link-time collisions because multiple
> arches use the same helper names.
>

Ok so have half a plan here now for the helper link-time namespace
problem. The top level HELPER() macro can be patched to glue() in an
architecture name set by cpu.h. The every use of HELPER(foo) will be
namespace collision free. The catch? Some arches mass-use literal
helper_foo for defs and calls. Fortunately ARM is well behaved and
only has about 4 usages so thats an easy convert. Microblaze has more.
It will be a reasonably simple (but tedious) scripted changed to
convert uses and definitions of helper_foo to HELPER(foo) but it saves
on the verbosity of having to go in and preface everything (all of
callsites, definitions and helper.h defs themselves).

Regards,
Peter

> A lowest common denomintor approach is taken on architecture specifics. E.g.
> TARGET_LONG is 64-bit, and the address space sizes and NUM_MMU_MODES is set
> to the maximum of all the supported arches.
>
> The remaining globally defined interfaces between core code and CPUs are
> QOMified per-cpu (P2)
>
> Microblaze translation needs a change pattern to allow conversion to 64-bit
> TARGET_LONG. Uses of TCGv need to be removed and explicited to 32-bit.
>
> This RFC will serve as a reference as I send bits and piece to the respective
> maintainers (many major subsystems are patched).
>
> No support for KVM, im not sure if a mix of TCG and KVM is supported even for
> a single arch? (which would be prerequisite to MA KVM).
>
> Depends (not heavily) on my on-list disas QOMification. Test instructions
> available on request. I have tested ARM & MB elfs handshaking through shared
> memory and both printfing to the same UART (verifying system level
> connectivity). -d in_asm works with the mix of disas arches comming out.
>
> Regards,
> Peter
>
> Peter Crosthwaite (34):
>   cpu-all: Prototype cpu_exec and cpu_signal_handler
>   tcg+qom: QOMify core CPU defintions
>   target-multi: Add
>   mb: Change target long to 64b
>   mb: cpu: Delete MMAP_SHIFT definition
>   mb: rename EXCP macros
>   mb: Remove ELF_MACHINE from cpu.h
>   mb: cpu.h: Move cpu-all include
>   mb: delete dummy prototypes
>   HACK: microblaze: rename clz helper
>   mb: cpu: Remove MMUx macros
>   mb: cpu: Move CPU_COMMON to front of env
>   mb: cpu: Change phys and virt address ranges.
>   mb: Use qomified tcg defintions
>   hw: mb: Explicitly include cpu.h for consumers
>   mb: cpu: Guard cpu_init definition for user mode
>   mb: cpu: Multi-define guard deep CPU specifics
>   mb: cpu-qom: Put the ENV first
>   mb: Enable multi-arch
>   configure: Unify arm and aarch64 disas configury
>   arm: Rename all exceptions
>   arm: Remove ELF_MACHINE from cpu.h
>   arm: cpu.h: Move cpu-all include
>   arm: delete dummy prototypes
>   arm: cpu: Move CPU_COMMON to front of env
>   arm: Use qomified tcg defintions
>   hw: arm: Explicitly include cpu.h for consumers
>   arm: cpu: Guard cpu_init definition for user mode
>   arm: cpu: Multi-define guard deep CPU specifics
>   arm: Enable multi-arch
>   arm: boot: Don't assume all CPUs are ARM
>   arm: xilinx_zynq: Add a microblaze
>   HACK: mb: boot: Assume using -firmware for mb software
>   HACK: mb: boot: Disable dtb load in multi-arch
>
>  Makefile.target                   |  10 +-
>  arch_init.c                       |   4 +-
>  configure                         |  24 +-
>  default-configs/multi-softmmu.mak |   3 +
>  hw/arm/armv7m.c                   |   2 +-
>  hw/arm/boot.c                     |   8 +-
>  hw/arm/strongarm.h                |   2 +
>  hw/arm/xilinx_zynq.c              |  13 +
>  hw/microblaze/boot.c              |  12 +-
>  hw/microblaze/boot.h              |   2 +
>  include/exec/cpu-all.h            |   9 +
>  include/hw/arm/arm.h              |   2 +
>  include/hw/arm/digic.h            |   2 +
>  include/hw/arm/exynos4210.h       |   2 +
>  include/hw/arm/omap.h             |   2 +
>  include/hw/arm/pxa.h              |   2 +
>  include/qom/cpu.h                 |  24 ++
>  include/sysemu/arch_init.h        |   1 +
>  linux-user/elfload.c              |   3 +
>  linux-user/main.c                 |  38 +--
>  qom/cpu.c                         |   6 +
>  softmmu_template.h                |   6 +
>  target-arm/cpu-qom.h              |   7 +
>  target-arm/cpu.c                  | 113 ++++++-
>  target-arm/cpu.h                  | 185 +++--------
>  target-arm/helper-a64.c           |  24 +-
>  target-arm/helper.c               |  56 ++--
>  target-arm/internals.h            |  36 +-
>  target-arm/op_helper.c            |  24 +-
>  target-arm/psci.c                 |   4 +-
>  target-arm/translate-a64.c        |  18 +-
>  target-arm/translate.c            |  55 ++--
>  target-arm/translate.h            |   4 +-
>  target-microblaze/cpu-qom.h       |  11 +-
>  target-microblaze/cpu.c           |  34 ++
>  target-microblaze/cpu.h           |  78 ++---
>  target-microblaze/helper.c        |  22 +-
>  target-microblaze/helper.h        |   2 +-
>  target-microblaze/op_helper.c     |  18 +-
>  target-microblaze/translate.c     | 669 
> +++++++++++++++++++-------------------
>  target-multi/Makefile.objs        |   1 +
>  target-multi/cpu-head.h           |  24 ++
>  target-multi/cpu.h                |  40 +++
>  target-multi/helper.h             |   2 +
>  target-multi/translate.c          |  15 +
>  target-multi/translate.h          |  10 +
>  translate-all.c                   |  47 ++-
>  47 files changed, 979 insertions(+), 697 deletions(-)
>  create mode 100644 default-configs/multi-softmmu.mak
>  create mode 100644 target-multi/Makefile.objs
>  create mode 100644 target-multi/cpu-head.h
>  create mode 100644 target-multi/cpu.h
>  create mode 100644 target-multi/helper.h
>  create mode 100644 target-multi/translate.c
>  create mode 100644 target-multi/translate.h
>
> --
> 1.9.1
>
>