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.
Changes in v4: - drop [PATCH v3 7/8] and limit maximum supported cpu number - chance 'fw load' to take second parameter for initrd load address - change default initrd load address for qemu-x86
Miao Yan (8): x86: qemu: add fw_cfg support x86: qemu: add a cpu uclass driver for qemu target x86: fix a typo in function name x86: use actual CPU number for allocating memory x86: qemu: add qemu_fwcfg_fdt_fixup() x86: qemu: fix up cpu node in device tree x86: qemu: adjust ramdisk load address x86: qemu: 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 | 57 +++++++ arch/x86/cpu/qemu/fw_cfg.c | 333 +++++++++++++++++++++++++++++++++++++++ arch/x86/cpu/qemu/fw_cfg.h | 108 +++++++++++++ arch/x86/cpu/qemu/qemu.c | 7 + arch/x86/dts/qemu-x86_i440fx.dts | 19 +-- arch/x86/dts/qemu-x86_q35.dts | 19 +-- doc/README.x86 | 35 +++- include/configs/qemu-x86.h | 13 ++ 10 files changed, 559 insertions(+), 46 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