Re: [PATCH v3 08/12] hw/nvram: NPCM7xx OTP device model

[Philippe Mathieu-Daudé]

On Fri, Jul 3, 2020 at 11:19 PM Havard Skinnemoen
<hskinnemoen@google.com> wrote:
>
> On Fri, Jul 3, 2020 at 2:07 PM Havard Skinnemoen <hskinnemoen@google.com> 
> wrote:
> >
> > On Fri, Jul 3, 2020 at 6:46 AM Philippe Mathieu-Daudé <f4bug@amsat.org> 
> > wrote:
> > >
> > > On 6/27/20 1:55 AM, Havard Skinnemoen wrote:
> > > > +static void npcm7xx_otp_realize(DeviceState *dev, Error **errp)
> > > > +{
> > > > +    NPCM7xxOTPClass *oc = NPCM7XX_OTP_GET_CLASS(dev);
> > > > +    NPCM7xxOTPState *s = NPCM7XX_OTP(dev);
> > > > +    SysBusDevice *sbd = &s->parent;
> > > > +
> > > > +    s->array = g_malloc0(NPCM7XX_OTP_ARRAY_BYTES);
> > >
> > > The possibility to reuse persistent OTP seems important.
> > > This can be added later of course.
> >
> > Agree, it's an important part of the behavior of the module. But it's
> > not essential to be able to boot a BMC firmware image, so I left it
> > out initially.
> >
> > > See simple example in hw/nvram/eeprom_at24c.c which use
> > > a BlockBackend so the OTP content is not lost after reset
> > > or migration.
> >
> > I'll take a look at that, thanks!
> >
> > > > +
> > > > +    memory_region_init_io(&s->mmio, OBJECT(s), oc->mmio_ops, s, "regs",
> > > > +                          NPCM7XX_OTP_REGS_SIZE);
> > > > +    sysbus_init_mmio(sbd, &s->mmio);
> > > > +}
> > > > +
> > > > +static void npcm7xx_otp_class_init(ObjectClass *klass, void *data)
> > > > +{
> > > > +    ResettableClass *rc = RESETTABLE_CLASS(klass);
> > > > +    DeviceClass *dc = DEVICE_CLASS(klass);
> > > > +
> > >
> > > Missing migration vmstate for NPCM7xxOTPState::regs[].
> >
> > Ah, you're right. This is probably true for most of the peripherals in
> > this series. I'll see if I can get it sorted out for the next
> > iteration.
>
> Btw, do you have any advice on how to test device migration? I'm not
> planning to do actual migration of BMCs in the near future, so I'm not
> sure if I'd notice if I get it wrong.

Peter Maydell described it very simply here:
https://translatedcode.wordpress.com/category/debugging-tricks/