Re: [PATCH v6 3/3] docs/system: riscv: Add pflash usage details

[Sunil V L <sunilvl@ventanamicro.com>]

On Wed, May 31, 2023 at 09:43:39AM -0700, Andrea Bolognani wrote:
> On Wed, May 31, 2023 at 07:53:00PM +0530, Sunil V L wrote:
> > +Using flash devices
> > +-------------------
> > +
> > +When KVM is not enabled, the first flash device (pflash0) can contain either
> > +the ROM code or S-mode payload firmware code. If the pflash0 contains the
> > +ROM code, -bios should be set to none. If -bios is not set to
> > +none, pflash0 is assumed to contain S-mode payload code.
> > +
> > +When KVM is enabled, pflash0 is always assumed to contain the S-mode payload
> > +firmware.
> > +
> > +Firmware images used for pflash should be of size 32 MiB.
> > +
> > +To boot as ROM code:
> > +
> > +.. code-block:: bash
> > +
> > +  $ qemu-system-riscv64 -bios none \
> > +     -blockdev node-name=pflash0,driver=file,read-only=on,filename=<rom_code> \
> > +     -M virt,pflash0=pflash0 \
> > +     ... other args ....
> > +
> > +To boot as read-only S-mode payload:
> > +
> > +.. code-block:: bash
> > +
> > +  $ qemu-system-riscv64 \
> > +     -blockdev node-name=pflash0,driver=file,read-only=on,filename=<s-mode_fw_code> \
> > +     -blockdev node-name=pflash1,driver=file,filename=<s-mode_fw_vars> \
> > +     -M virt,pflash0=pflash0,pflash1=pflash1 \
> > +     ... other args ....
> > +
> > +To boot as read-only S-mode payload in KVM guest:
> > +
> > +.. code-block:: bash
> > +
> > +  $ qemu-system-riscv64 \
> > +     -blockdev node-name=pflash0,driver=file,read-only=on,filename=<s-mode_fw_code> \
> > +     -blockdev node-name=pflash1,driver=file,filename=<s-mode_fw_vars> \
> > +     -M virt,pflash0=pflash0,pflash1=pflash1 \
> > +     --enable-kvm \
> > +     ... other args ....
> 
> I feel that this, while accurate, has gotten more complicated than it
> needs to be. We're also putting the least common scenario front and
> center instead of opening with the one that most people are going to
> be using.
> 
> Below is how I suggest reworking it. What do you think?
> 
> 
> 
> Using flash devices
> -------------------
> 
> By default, the first flash device (pflash0) is expected to contain
> S-mode firmware code. It can be configured as read-only, with the
> second flash device (pflash1) available to store configuration data.
> 
> For example, booting edk2 looks like
> 
> ..code-block:: bash
> 
>   $ qemu-system-riscv64 \
>      -blockdev node-name=pflash0,driver=file,read-only=on,filename=<edk2_code> \
>      -blockdev node-name=pflash1,driver=file,filename=<edk2_vars> \
>      -M virt,pflash0=pflash0,pflash1=pflash1 \
>      ... other args ....
> 
> For TCG guests only, it is also possible to boot M-mode firmware from
> the first flash device (pflash0) by additionally passing ``-bios
> none``, as in
> 
> ..code-block:: bash
> 
>   $ qemu-system-riscv64 \
>      -bios none \
>      -blockdev node-name=pflash0,driver=file,read-only=on,filename=<m_mode_code>
> \
>      -M virt,pflash0=pflash0 \
>      ... other args ....
> 
> Firmware images used for pflash must be exactly 32 MiB in size.
> 
Hi Andrea,

This looks great! Thank you very much. Unless I see an objection, I will
use this text in the next revision of the series tomorrow.

Thanks!
Sunil