Re: [PATCH v1 5/6] riscv/virt: Add the PFlash CFI01 device

[Alistair Francis]

On Mon, Sep 23, 2019 at 2:46 PM Peter Maydell <address@hidden> wrote:
>
> On Fri, 20 Sep 2019 at 23:23, Alistair Francis <address@hidden> wrote:
> > On Thu, Sep 19, 2019 at 10:15 PM Bin Meng <address@hidden> wrote:
> > > I don't think we should mirror what is used on ARM virt board to
> > > create 2 flash for sifive_u. For ARM virt, there are 2 flashes because
> > > they need distinguish secure and non-secure. For sifive_u, only one is
> > > enough.
> >
> > I went back and forward about 1 or 2. Two seems more usable as maybe
> > someone wants to include two pflash files? The Xilinx machine also has
> > two so I'm kind of used to 2, but I'm not really fussed.
>
> One of the reasons for having 2 on the Arm board (we do this
> even if we're not supporting secure vs non-secure) is that
> then you can use one for a fixed read-only BIOS image (backed
> by a file on the host filesystem shared between all VMs), and
> one backed by a read-write per-VM file providing permanent
> storage for BIOS environment variables. Notably UEFI likes to
> work this way, but the idea applies in theory to other
> boot loader or BIOSes I guess.

This seems like a good reason to have two and there isn't really a
disadvantage so I have kept it with two.

>
> I would suggest also checking with Markus that your code
> for instantiating the flash devices follows the current
> recommendations so the backing storage can be configured
> via -blockdev. (This is a fairly recent change from June or
> so; current-in-master virt and sbsa boards provide an example
> of doing the right thing, I think.)

I have updated the code to more closely match the ARM virt machine, so
I think I'm doing it correctly.

Alistair

>
> thanks
> -- PMM