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

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Hi Stewart,

On 15/10/2018 23:26, Stewart Hildebrand wrote:
> "The Image must be placed text_offset bytes from a 2MB aligned base
> address anywhere in usable system RAM and called there."
> 
> 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.
> 
> This fixes a boot failure for Xen AArch64.
> 
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@dornerworks.com>
> ---
>  hw/arm/boot.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/hw/arm/boot.c b/hw/arm/boot.c
> index 20c71d7d96..559ddbcd53 100644
> --- a/hw/arm/boot.c
> +++ b/hw/arm/boot.c
> @@ -919,6 +919,16 @@ static uint64_t load_aarch64_image(const char *filename, hwaddr mem_base,
>          memcpy(&hdrvals, buffer + ARM64_TEXT_OFFSET_OFFSET, sizeof(hdrvals));
>          if (hdrvals[1] != 0) {
>              kernel_load_offset = le64_to_cpu(hdrvals[0]);
> +
> +            /* 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...

> +                kernel_load_offset += 2 << 20;

You can use += 2 * MiB; which is easier to review.

> +            }
>          }
>      }
>  
>