Re: [PATCH v3] hw/riscv: virt: Assume M-mode FW in pflash0 only when "-bios none"

[Alistair Francis <alistair23@gmail.com>]

On Tue, May 23, 2023 at 8:29 PM Sunil V L <sunilvl@ventanamicro.com> wrote:
>
> Currently, virt machine supports two pflash instances each with
> 32MB size. However, the first pflash is always assumed to
> contain M-mode firmware and reset vector is set to this if
> enabled. Hence, for S-mode payloads like EDK2, only one pflash
> instance is available for use. This means both code and NV variables
> of EDK2 will need to use the same pflash.
>
> The OS distros keep the EDK2 FW code as readonly. When non-volatile
> variables also need to share the same pflash, it is not possible
> to keep it as readonly since variables need write access.
>
> To resolve this issue, the code and NV variables need to be separated.
> But in that case we need an extra flash. Hence, modify the convention
> such that pflash0 will contain the M-mode FW only when "-bios none"
> option is used. Otherwise, pflash0 will contain the S-mode payload FW.
> This enables both pflash instances available for EDK2 use.
>
> Example usage:
> 1) pflash0 containing M-mode FW
> qemu-system-riscv64 -bios none -pflash <mmode_fw> -machine virt
> or
> qemu-system-riscv64 -bios none \
> -drive file=<mmode_fw>,if=pflash,format=raw,unit=0 -machine virt
>
> 2) pflash0 containing S-mode payload like EDK2
> qemu-system-riscv64 -pflash <smode_fw_code> -pflash <smode_vars> -machine  virt
> or
> qemu-system-riscv64 -bios <opensbi_fw> \
> -pflash <smode_fw_code> \
> -pflash <smode_vars> \
> -machine  virt
> or
> qemu-system-riscv64 -bios <opensbi_fw> \
> -drive file=<smode_fw_code>,if=pflash,format=raw,unit=0,readonly=on \
> -drive file=<smode_fw_vars>,if=pflash,format=raw,unit=1 \
> -machine virt
>
> Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
> Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>
> The issue is reported at
> https://salsa.debian.org/qemu-team/edk2/-/commit/c345655a0149f64c5020bfc1e53c619ce60587f6
>
> The patch is based on Alistair's riscv-to-apply.next branch.
>
> Changes since v2:
>         1) Reverted v2 changes and used v1 approach so that pflash0 can be used
>            for code and pflash1 for variable store.
>         2) Rebased to latest riscv-to-apply.next branch.
>         3) Added documentation for pflash usage.
>
> Changes since v1:
>         1) Simplified the fix such that it doesn't break current EDK2.
>
>  docs/system/riscv/virt.rst | 33 ++++++++++++++++++++++++
>  hw/riscv/virt.c            | 51 ++++++++++++++------------------------
>  2 files changed, 52 insertions(+), 32 deletions(-)
>
> diff --git a/docs/system/riscv/virt.rst b/docs/system/riscv/virt.rst
> index 4b16e41d7f..4ac0d38fdf 100644
> --- a/docs/system/riscv/virt.rst
> +++ b/docs/system/riscv/virt.rst
> @@ -53,6 +53,39 @@ with the default OpenSBI firmware image as the -bios. It also supports
>  the recommended RISC-V bootflow: U-Boot SPL (M-mode) loads OpenSBI fw_dynamic
>  firmware and U-Boot proper (S-mode), using the standard -bios functionality.
>
> +Using flash devices
> +-------------------
> +
> +The first flash device (pflash0) can contain either ROM code like Oreboot
> +or S-mode payload firmware code like EDK2. If the pflash0 contains the
> +ROM code, -bios should be set to none. Otherwise, pflash0 is assumed to
> +contain S-mode payload code.
> +
> +Firmware images used for pflash should be of size 32M.
> +
> +To boot as ROM code like Oreboot:
> +
> +.. code-block:: bash
> +
> +  $ qemu-system-riscv64 -bios none -pflash <rom_code_image> \
> +       ... other args ....
> +
> +To boot as S-mode payload like EDK2:
> +
> +.. code-block:: bash
> +
> +  $ qemu-system-riscv64 -pflash <s-mode_fw_code> -pflash <smode_fw_vars> \
> +       ... other args ....
> +
> +To boot as read-only S-mode payload like EDK2:
> +
> +.. code-block:: bash
> +
> +  $ qemu-system-riscv64 -bios <opensbi_fw> \
> +       -drive file=<smode_fw_code>,if=pflash,format=raw,unit=0,readonly=on \
> +       -drive file=<smode_fw_vars>,if=pflash,format=raw,unit=1 \
> +       ... other args ....
> +
>  Machine-specific options
>  ------------------------
>
> diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> index 4e3efbee16..1187a60d6e 100644
> --- a/hw/riscv/virt.c
> +++ b/hw/riscv/virt.c
> @@ -1245,7 +1245,7 @@ static void virt_machine_done(Notifier *notifier, void *data)
>      target_ulong firmware_end_addr, kernel_start_addr;
>      const char *firmware_name = riscv_default_firmware_name(&s->soc[0]);
>      uint32_t fdt_load_addr;
> -    uint64_t kernel_entry;
> +    uint64_t kernel_entry = 0;
>
>      /*
>       * Only direct boot kernel is currently supported for KVM VM,
> @@ -1266,42 +1266,29 @@ static void virt_machine_done(Notifier *notifier, void *data)
>      firmware_end_addr = riscv_find_and_load_firmware(machine, firmware_name,
>                                                       start_addr, NULL);
>
> -    if (drive_get(IF_PFLASH, 0, 1)) {
> -        /*
> -         * S-mode FW like EDK2 will be kept in second plash (unit 1).
> -         * When both kernel, initrd and pflash options are provided in the
> -         * command line, the kernel and initrd will be copied to the fw_cfg
> -         * table and opensbi will jump to the flash address which is the
> -         * entry point of S-mode FW. It is the job of the S-mode FW to load
> -         * the kernel and initrd using fw_cfg table.
> -         *
> -         * If only pflash is given but not -kernel, then it is the job of
> -         * of the S-mode firmware to locate and load the kernel.
> -         * In either case, the next_addr for opensbi will be the flash address.
> -         */
> -        riscv_setup_firmware_boot(machine);
> -        kernel_entry = virt_memmap[VIRT_FLASH].base +
> -                       virt_memmap[VIRT_FLASH].size / 2;
> -    } else if (machine->kernel_filename) {
> +    if (drive_get(IF_PFLASH, 0, 0)) {
> +        if (machine->firmware && !strcmp(machine->firmware, "none")) {
> +            /*
> +             * Pflash was supplied but bios is none, let's overwrite the
> +             * address we jump to after reset to the base of the flash.
> +             */
> +            start_addr = virt_memmap[VIRT_FLASH].base;
> +        } else {
> +            /*
> +             * Pflash was supplied but bios is not none. In this case,
> +             * base of the flash would contain S-mode payload.
> +             */
> +            riscv_setup_firmware_boot(machine);
> +            kernel_entry = virt_memmap[VIRT_FLASH].base;
> +        }
> +    }
> +
> +    if (machine->kernel_filename && !kernel_entry) {
>          kernel_start_addr = riscv_calc_kernel_start_addr(&s->soc[0],
>                                                           firmware_end_addr);
>
>          kernel_entry = riscv_load_kernel(machine, &s->soc[0],
>                                           kernel_start_addr, true, NULL);
> -    } else {
> -       /*
> -        * If dynamic firmware is used, it doesn't know where is the next mode
> -        * if kernel argument is not set.
> -        */
> -        kernel_entry = 0;
> -    }
> -
> -    if (drive_get(IF_PFLASH, 0, 0)) {
> -        /*
> -         * Pflash was supplied, let's overwrite the address we jump to after
> -         * reset to the base of the flash.
> -         */
> -        start_addr = virt_memmap[VIRT_FLASH].base;
>      }
>
>      fdt_load_addr = riscv_compute_fdt_addr(memmap[VIRT_DRAM].base,
> --
> 2.34.1
>
>