Re: [PATCH v2] hw/riscv: virt: Assume M-mode FW in pflash0 only when "-bios none"

[Sunil V L]

Hi Alistair,

On Tue, Apr 25, 2023 at 03:55:45PM +0530, Sunil V L 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_vars> -pflash <smode_fw_code> -machine  
> virt
> or
> qemu-system-riscv64 -bios <opensbi_fw> \
> -pflash <smode_fw_vars> \
> -pflash <smode_fw_code> \
> -machine  virt
> or
> qemu-system-riscv64 -bios <opensbi_fw> \
> -drive file=<smode_fw_vars>,if=pflash,format=raw,unit=0 \
> -drive file=<smode_fw_code>,if=pflash,format=raw,unit=1,readonly=on  \
> -machine virt
> 
> Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
> Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
> ---
> 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 v1:
>       1) Simplified the fix such that it doesn't break current EDK2.
>
Could you please help reviewing this patch? This was sent when you were
out of office.

Thanks,
Sunil 
>  hw/riscv/virt.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> index 4e3efbee16..ca445d3d02 100644
> --- a/hw/riscv/virt.c
> +++ b/hw/riscv/virt.c
> @@ -1296,10 +1296,11 @@ static void virt_machine_done(Notifier *notifier, 
> void *data)
>          kernel_entry = 0;
>      }
>  
> -    if (drive_get(IF_PFLASH, 0, 0)) {
> +    if (drive_get(IF_PFLASH, 0, 0) &&
> +                 machine->firmware && !strcmp(machine->firmware, "none")) {
>          /*
> -         * Pflash was supplied, let's overwrite the address we jump to after
> -         * reset to the base of the flash.
> +         * Pflash0 was supplied with "-bios none", let's overwrite the 
> address
> +         * we jump to after reset to the base of the flash.
>           */
>          start_addr = virt_memmap[VIRT_FLASH].base;
>      }
> -- 
> 2.34.1
>