Re: [Xen-devel] [PATCH v4 5/5] fix: add multiboot2 protocol support for EFI platforms

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.01.17 at 15:17, <cardoe@xxxxxxxxxx> wrote:
> This should be squashed into the 4/4 patch 'x86: add multiboot2 protocol
> support for EFI platforms'.
> 
> - fix incorrect assembly (identified by Andrew Cooper)
> - fix issue where the trampoline size was left as 0 and the
>   way the memory is allocated for the trampolines we would go to
>   the end of an available section and then subtract off the size
>   to decide where to place it. The end result was that we would
>   always copy the trampolines and the 32-bit stack into some
>   form of reserved memory after the conventional region we
>   wanted to put things into. On some systems this did not
>   manifest as a crash while on others it did. Reworked the
>   changes to always reserve 64kb for both the stack and the size
>   of the trampolines. Added a build time assert to make sure we have
>   enough room always.
> 
> Signed-off-by: Doug Goldstein <cardoe@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
with ...

> --- a/xen/arch/x86/xen.lds.S
> +++ b/xen/arch/x86/xen.lds.S
> @@ -333,3 +333,10 @@ ASSERT(IS_ALIGNED(trampoline_start, 4), 
> "trampoline_start misaligned")
>  ASSERT(IS_ALIGNED(trampoline_end,   4), "trampoline_end misaligned")
>  ASSERT(IS_ALIGNED(__bss_start,      8), "__bss_start misaligned")
>  ASSERT(IS_ALIGNED(__bss_end,        8), "__bss_end misaligned")
> +
> +/* The trampolines and the low memory stack must fit in 64kb. In testing
> + * the low memory stack never exceeded 1kb so just require that the
> + * trampolines fit in 63kb, leaving 1kb for the stack.
> + */
> +ASSERT((trampoline_end - trampoline_start) < KB(63),
> +    "not enough room for trampolines and low memory stack")

... the comment style here fixed (which could be done upon commit
or when Daniel merges this back into his series).

Jan


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