On 21/08/2024 2:32 pm, Frediano Ziglio wrote:
> We need to write in some location but no reasons to not
> trying to restore what we potentially overwrote.
>
> Signed-off-by: Frediano Ziglio <[email protected]>

Please follow how Linux does this.

e.g.
https://lore.kernel.org/xen-devel/[email protected]/

Specifically, ...

> ---
>  xen/arch/x86/boot/head.S | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
> index d8ac0f0494..3e1e9e05b6 100644
> --- a/xen/arch/x86/boot/head.S
> +++ b/xen/arch/x86/boot/head.S
> @@ -418,13 +418,17 @@ __pvh_start:
>           * absolute stack address as the native path, for lack of a better
>           * alternative.
>           */

... the reasoning in this comment here is incorrect for non-BIOS
systems, and causes memory corruption for Coreboot based boot.

I've been meaning to fix it for ages, but seeing as you're changing it... :)

The first field under %ebx in a boot ABI we recognise is a much better
choice that an arbitrary location in the first page of memory.

~Andrew

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