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

From: Peter Maydell
Subject: Re: [PATCH v1 5/6] riscv/virt: Add the PFlash CFI01 device
Date: Mon, 23 Sep 2019 22:46:17 +0100

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.

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.)

-- PMM

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