[U-Boot] [PATCH 0/7] add fw_cfg interface support for qemu-x86 targets

[Saket Sinha]

Hi Miao,

Thanks for the patches.

I made an initial attempt to support the fw_cfg in U-boot for QEMU to
get acpi tables by fw_cfg for qemu-x86 targets.

The idea was if we find acpi tables in fw_cfg try loading them,
otherwise fallback to the builtin acpi tables.

The patch was dropped mainly because ACPI tables loaded by fw_cfg had
some issues which I could not figure out.
The patches were discussed(me, Simon and Bin) offline(off the mailing
list), so I am forwarding it to you and the community.

If we can collaborate the patches in the sense that we are able to
load ACPI tables(and other tables) successfully, it would be great.


Regards,
Saket Sinha


On Mon, Dec 28, 2015 at 2:48 PM, Miao Yan <yanmiaobest at gmail.com> wrote:
> The fw_cfg interface provided by QEMU allow guests to retrieve various information
> about the system, e.g. cpu number, variaous firmware data, kernel setup, etc. The
> fw_cfg interface can be accessed through 3 IO ports (on x86), using x86 in/out
> instructions.
>
>   - 0x510: select configuration items to access
>   - 0x511: reading this port will return data selected in 0x510
>   - 0x514: this can be used to detect if DMA interface is available
>
> If fw_cfg DMA interface is available, it can be used to accelerate
> accesses.
>
> This patchset adds the following supports for qemu-x86 targets:
>
>   + the fw_cfg driver itself
>
>   + add a U-Boot command 'fw' to support direct accessing kernel informtion
>     from fw_cfg interface, this saves the time of loading them from hard disk or
>     network again, through emulated devices.
>
>   + use fw_cfg to get cpu number at runtime, so smp boot no longer relies on
>     the cpu node hard-coded in dts files.
>
> Miao Yan (7):
>   x86: qemu: add fw_cfg support
>   x86: qemu: add a cpu uclass driver for qemu target
>   x86: fix a typo in function name
>   x86: qemu: use actual CPU number for allocating memory
>   x86: qemu: add qemu_fwcfg_fdt_fixup()
>   x86: qemu: fixup cpu node in device tree
>   qemu-x86: add documentaion for the fw_cfg interface
>
>  arch/x86/cpu/mp_init.c           |  12 +-
>  arch/x86/cpu/qemu/Makefile       |   2 +-
>  arch/x86/cpu/qemu/cpu.c          |  58 ++++++++
>  arch/x86/cpu/qemu/fw_cfg.c       | 281 +++++++++++++++++++++++++++++++++++++++
>  arch/x86/cpu/qemu/fw_cfg.h       |  85 ++++++++++++
>  arch/x86/cpu/qemu/qemu.c         |   7 +
>  arch/x86/dts/qemu-x86_i440fx.dts |  18 +--
>  arch/x86/dts/qemu-x86_q35.dts    |  19 +--
>  doc/README.x86                   |  36 ++++-
>  9 files changed, 473 insertions(+), 45 deletions(-)
>  create mode 100644 arch/x86/cpu/qemu/cpu.c
>  create mode 100644 arch/x86/cpu/qemu/fw_cfg.c
>  create mode 100644 arch/x86/cpu/qemu/fw_cfg.h
>
> --
> 1.9.1
>
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