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Date: Tue, 16 Oct 2018 11:02:00 +0100
From: Andre Przywara <andre.przywara@arm.com>
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Subject: Re: [Qemu-devel] [PATCH] hw/arm/boot: Increase compliance with
 kernel arm64 boot protocol.
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To: Stewart Hildebrand <Stewart.Hildebrand@dornerworks.com>
Cc: Philippe =?UTF-8?B?TWF0aGlldS1EYXVkw6k=?= <philmd@redhat.com>, "qemu-arm@nongnu.org" <qemu-arm@nongnu.org>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Julien Grall <julien.grall@arm.com>, Peter Maydell <peter.maydell@linaro.org>

On Tue, 16 Oct 2018 01:19:35 +0000
Stewart Hildebrand <Stewart.Hildebrand@dornerworks.com> wrote:

Hi,

Stewart, thanks a lot for picking this up!

> On Monday, October 15, 2018 6:05 PM, Philippe Mathieu-Daud=C3=A9 wrote:
> > Hi Stewart,
> >=20
> > On 15/10/2018 23:26, Stewart Hildebrand wrote: =20
> > > +            /* For the virt board, we write our startup
> > > "bootloader" at the very
> > > +             * bottom of RAM, so that bit can't be used for the
> > > image. To avoid
> > > +             * overlap in case the image requests to be loaded
> > > at an offset
> > > +             * smaller than our bootloader, we increment the
> > > load offset to the
> > > +             * next 2MB.
> > > +             */
> > > +            if (kernel_load_offset < FIXUP_MAX) { =20
> >=20
> > I don't understand how this is related to FIXUP_MAX... =20
>=20
> You're right, my apologies, it's not directly related.
> write_bootloader() calculates the size of the bootloader like so:
>     len =3D 0;
>     while (insns[len].fixup !=3D FIXUP_TERMINATOR) {
>         len++;
>     }
>=20
> The size of the bootloader then would be len * sizeof(uint32_t)
>=20
> It would be nice not to have to repeat that logic in
> load_aarch64_image(). I'll send out a v2 after I take some time to
> wrap my head around it...=20

I wonder if this could be done much easier, since TEXT_OFFSET must
actually be page aligned. So all we would need is an *upper bound* for
the bootloader size, as long as that is below 4K we wouldn't even loose
anything.

Cheers,
Andre.

> >  =20
> > > +                kernel_load_offset +=3D 2 << 20; =20
> >=20
> > You can use +=3D 2 * MiB; which is easier to review. =20
>=20
> OK, I will include this in v2.