Re: [Xen-devel] [PATCH v12 05/10] x86: add multiboot2 protocol support for EFI platforms

[Doug Goldstein <cardoe@xxxxxxxxxx>]

On 1/19/17 8:34 PM, Daniel Kiper wrote:

> diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
> index 62c010e..c1285ad 100644
> --- a/xen/arch/x86/efi/efi-boot.h
> +++ b/xen/arch/x86/efi/efi-boot.h


> +
> +    efi_exit_boot(ImageHandle, SystemTable);
> +
> +    /* Return highest allocated memory address below 1 MiB. */
> +    return cfg.addr + cfg.size;

So my comment about overwriting memory on 02/10 was spot on but made the
incorrect conclusion that it was before hand and not after. And here's
the issue. I believe what you meant to do was:

return cfg.addr + MBI_SIZE;

I can't see how this booted for you with OVMF because for all the
different versions I've tried with the original code its writing over
reserved memory that QEMU uses for the graphics buffers. Which
immediately results in the trampolines being overwritten with console data.

-- 
Doug Goldstein

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