Re: [Qemu-devel] [PATCH v1 2/2] hw/riscv: Load OpenSBI as the default firmware

[Guenter Roeck <linux@roeck-us.net>]

On Mon, Jul 08, 2019 at 11:49:40AM -0700, Alistair Francis wrote:
> If the user hasn't specified a firmware to load (with -bios) or
> specified no bios (with -bios none) then load OpenSBI by default. This
> allows users to boot a RISC-V kernel with just -kernel.
> 
> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
> Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
> Tested-by: Bin Meng <bmeng.cn@gmail.com>
> ---
>  hw/riscv/boot.c         | 49 +++++++++++++++++++++++++++++++++++++++++
>  hw/riscv/sifive_u.c     |  7 +++---
>  hw/riscv/virt.c         | 11 ++++++---
>  include/hw/riscv/boot.h |  3 +++
>  qemu-deprecated.texi    | 20 +++++++++++++++++
>  5 files changed, 84 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/riscv/boot.c b/hw/riscv/boot.c
> index ff023f42d0..c7d72f682f 100644
> --- a/hw/riscv/boot.c
> +++ b/hw/riscv/boot.c
> @@ -18,6 +18,7 @@
>   */
>  
>  #include "qemu/osdep.h"
> +#include "qemu-common.h"
>  #include "qemu/units.h"
>  #include "qemu/error-report.h"
>  #include "exec/cpu-defs.h"
> @@ -32,6 +33,54 @@
>  # define KERNEL_BOOT_ADDRESS 0x80200000
>  #endif
>  
> +void riscv_find_and_load_firmware(MachineState *machine,
> +                                  const char *default_machine_firmware,
> +                                  hwaddr firmware_load_addr)
> +{
> +    char *firmware_filename;
> +
> +    if (!machine->firmware) {
> +        /*
> +         * The user didn't specify -bios.
> +         * At the moment we default to loading nothing when this hapens.
> +         * In the future this defaul will change to loading the prebuilt
> +         * OpenSBI firmware. Let's warn the user and then continue.
> +        */
> +        warn_report("No -bios option specified. Not loading a firmware.");
> +        warn_report("This default will change in QEMU 4.3. Please use the " \
> +                    "-bios option to aviod breakages when this happens.");
> +        warn_report("See QEMU's deprecation documentation for details");
> +        return;
> +    }
> +
> +    if (!strcmp(machine->firmware, "default")) {
> +        /*
> +         * The user has specified "-bios default". That means we are going to
> +         * load the OpenSBI binary included in the QEMU source.
> +         *
> +         * We can't load the binary by default as it will break existing users
> +         * as users are already loading their own firmware.
> +         *
> +         * Let's try to get everyone to specify the -bios option at all times,
> +         * so then in the future we can make "-bios default" the default option
> +         * if no -bios option is set without breaking anything.
> +         */
> +        firmware_filename = qemu_find_file(QEMU_FILE_TYPE_BIOS,
> +                                           default_machine_firmware);

This can return NULL if the file is not found (such as after a bad install) ...

> +    } else {
> +        firmware_filename = machine->firmware;
> +    }
> +
> +    if (strcmp(firmware_filename, "none")) {

... which will then crash here.

> +        /* If not "none" load the firmware */
> +        riscv_load_firmware(firmware_filename, firmware_load_addr);
> +    }
> +
> +    if (!strcmp(machine->firmware, "default")) {
> +        g_free(firmware_filename);
> +    }
> +}
> +
>  target_ulong riscv_load_firmware(const char *firmware_filename,
>                                   hwaddr firmware_load_addr)
>  {
> diff --git a/hw/riscv/sifive_u.c b/hw/riscv/sifive_u.c
> index ca53a9290d..71b8083c05 100644
> --- a/hw/riscv/sifive_u.c
> +++ b/hw/riscv/sifive_u.c
> @@ -49,6 +49,8 @@
>  
>  #include <libfdt.h>
>  
> +#define BIOS_FILENAME "opensbi-riscv64-sifive_u-fw_jump.bin"
> +
>  static const struct MemmapEntry {
>      hwaddr base;
>      hwaddr size;
> @@ -269,9 +271,8 @@ static void riscv_sifive_u_init(MachineState *machine)
>      /* create device tree */
>      create_fdt(s, memmap, machine->ram_size, machine->kernel_cmdline);
>  
> -    if (machine->firmware) {
> -        riscv_load_firmware(machine->firmware, memmap[SIFIVE_U_DRAM].base);
> -    }
> +    riscv_find_and_load_firmware(machine, BIOS_FILENAME,
> +                                 memmap[SIFIVE_U_DRAM].base);
>  
>      if (machine->kernel_filename) {
>          riscv_load_kernel(machine->kernel_filename);
> diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> index ecdc77d728..25faf3b417 100644
> --- a/hw/riscv/virt.c
> +++ b/hw/riscv/virt.c
> @@ -44,6 +44,12 @@
>  
>  #include <libfdt.h>
>  
> +#if defined(TARGET_RISCV32)
> +# define BIOS_FILENAME "opensbi-riscv32-virt-fw_jump.bin"
> +#else
> +# define BIOS_FILENAME "opensbi-riscv64-virt-fw_jump.bin"
> +#endif
> +
>  static const struct MemmapEntry {
>      hwaddr base;
>      hwaddr size;
> @@ -399,9 +405,8 @@ static void riscv_virt_board_init(MachineState *machine)
>      memory_region_add_subregion(system_memory, memmap[VIRT_MROM].base,
>                                  mask_rom);
>  
> -    if (machine->firmware) {
> -        riscv_load_firmware(machine->firmware, memmap[VIRT_DRAM].base);
> -    }
> +    riscv_find_and_load_firmware(machine, BIOS_FILENAME,
> +                                 memmap[VIRT_DRAM].base);
>  
>      if (machine->kernel_filename) {
>          uint64_t kernel_entry = riscv_load_kernel(machine->kernel_filename);
> diff --git a/include/hw/riscv/boot.h b/include/hw/riscv/boot.h
> index daa179b600..d56f2ae3eb 100644
> --- a/include/hw/riscv/boot.h
> +++ b/include/hw/riscv/boot.h
> @@ -20,6 +20,9 @@
>  #ifndef RISCV_BOOT_H
>  #define RISCV_BOOT_H
>  
> +void riscv_find_and_load_firmware(MachineState *machine,
> +                                  const char *default_machine_firmware,
> +                                  hwaddr firmware_load_addr);
>  target_ulong riscv_load_firmware(const char *firmware_filename,
>                                   hwaddr firmware_load_addr);
>  target_ulong riscv_load_kernel(const char *kernel_filename);
> diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
> index c90b08d553..fff07bb2a3 100644
> --- a/qemu-deprecated.texi
> +++ b/qemu-deprecated.texi
> @@ -121,6 +121,26 @@ the backing storage specified with @option{-mem-path} can actually provide
>  the guest RAM configured with @option{-m} and QEMU will fail to start up if
>  RAM allocation is unsuccessful.
>  
> +@subsection RISC-V -bios (since 4.1)
> +
> +QEMU 4.1 introduced support for the -bios option in QEMU for RISC-V for the
> +RISC-V virt machine and sifive_u machine.
> +
> +QEMU 4.1 has no changes to the default behaviour to avoid breakages. This
> +default will change in a future QEMU release, so please prepare now. All users
> +of the virt or sifive_u machine must change their command line usage.
> +
> +QEMU 4.1 has three options, please migrate to one of these three:
> + 1. ``-bios none`` - This is the current default behavior if no -bios option
> +      is included. QEMU will not automatically load any firmware. It is up
> +      to the user to load all the images they need.
> + 2. ``-bios default`` - In a future QEMU release this will become the default
> +      behaviour if no -bios option is specified. This option will load the
> +      default OpenSBI firmware automatically. The firmware is included with
> +      the QEMU release and no user interaction is required. All a user needs
> +      to do is specify the kernel they want to boot with the -kernel option
> + 3. ``-bios <file>`` - Tells QEMU to load the specified file as the firmwrae.
> +
>  @section QEMU Machine Protocol (QMP) commands
>  
>  @subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0)