Re: [Qemu-devel] [PATCH] hw/arm/boot: Increase compliance with kernel arm64 boot protocol.

[Andre Przywara <andre.przywara@arm.com>]

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-Daudé wrote:
> > Hi Stewart,
> > 
> > On 15/10/2018 23:26, Stewart Hildebrand wrote:  
> > > +            /* 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) {  
> > 
> > I don't understand how this is related to FIXUP_MAX...  
> 
> You're right, my apologies, it's not directly related.
> write_bootloader() calculates the size of the bootloader like so:
>     len = 0;
>     while (insns[len].fixup != FIXUP_TERMINATOR) {
>         len++;
>     }
> 
> The size of the bootloader then would be len * sizeof(uint32_t)
> 
> 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... 

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.

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