Re: [Qemu-devel] [PATCH v7 2/2] hw/arm: Add arm SBSA reference machine, devices part

[Hongbo Zhang <hongbo.zhang@linaro.org>]

On Wed, 8 May 2019 at 21:59, Markus Armbruster <armbru@redhat.com> wrote:
>
> Peter Maydell <peter.maydell@linaro.org> writes:
>
> > On Thu, 18 Apr 2019 at 05:05, Hongbo Zhang <hongbo.zhang@linaro.org> wrote:
> >>
> >> Following the previous patch, this patch adds peripheral devices to the
> >> newly introduced SBSA-ref machine.
> >>
> >> Signed-off-by: Hongbo Zhang <hongbo.zhang@linaro.org>
> >> ---
> >>  hw/arm/sbsa-ref.c | 451 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >>  1 file changed, 451 insertions(+)
> >
> > Some fairly minor comments on this one.
> >
> >> +static void create_flash(const SBSAMachineState *vms,
> >> +                         MemoryRegion *sysmem,
> >> +                         MemoryRegion *secure_sysmem)
> >> +{
> >> +    /*
> >> +     * Create one secure and nonsecure flash devices to fill SBSA_FLASH
> >> +     * space in the memmap, file passed via -bios goes in the first one.
> >> +     */
> >> +    hwaddr flashsize = vms->memmap[SBSA_FLASH].size / 2;
> >> +    hwaddr flashbase = vms->memmap[SBSA_FLASH].base;
> >> +
> >> +    create_one_flash("sbsa-ref.flash0", flashbase, flashsize,
> >> +                     bios_name, secure_sysmem);
> >> +    create_one_flash("sbsa-ref.flash1", flashbase + flashsize, flashsize,
> >> +                     NULL, sysmem);
> >> +}
> >
> > I think Markus might have an opinion on the best way to create
> > flash devices on a new board model. Is "just create two flash
> > devices the way the virt board does" the right thing?
>
> Short answer: create flash devices the way the ARM virt board does now,
> after commit e0561e60f17, merged into master today.  Possibly less
> backward compatibility stuff you don't need.  As is, your patch creates
> them the way the ARM virt board did before commit e0561e60f17.  Please
> consider updating.
>
> Longer answer:
>
> The old way to configure block backends is -drive.
>
> The newer -blockdev is more flexible.  Libvirt is in the process of
> transitioning from -drive to -blockdev entirely.  Other users with
> similar needs for flexibility may do the same.  We hope to deprecate
> -drive eventually.
>
> The traditional way to configure onboard flash is -drive if=pflash.
> Works, but we need a way to configure with -blockdev for full
> flexibility, and to support libvirt ditching -drive entirely.
>
> I recently improved the i386 PC machine types (commit ebc29e1beab) and
> the ARM virt machine types (commit e0561e60f17) to support flash
> configuration with -blockdev.
>
> I recommend new boards support flash configuration with -blockdev from
> the start.
>
> Questions?

Sorry for the late response.
Thank you for the detailed explanation, and I'll follow the new
pattern in my next version of patch which will be sent out in a few
days.