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Re: [PATCH v1.1 08/22] x86/traps: Introduce percpu_early_traps_init() and set up exception handling earlier
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 15 Aug 2025 11:24:09 +0200
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Fri, 15 Aug 2025 09:24:19 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 14.08.2025 20:07, Andrew Cooper wrote:
> As things stand, we set up AP/S3 exception handling marginally after the
> fragile activity of setting up shadow stacks. Shadow stack setup is going to
> get more complicated under FRED.
>
> Introduce percpu_early_traps_init() and call it ahead of setting up shadow
> stacks. To start with, call load_system_tables() which is sufficient to set
> up full exception handling.
>
> In order to handle exceptions, current and the speculation controls needs to
> work. cpu_smpboot_alloc() already constructs some of the AP's top-of-stack
> block, so have it set up a little more. Zero the whole structure to subsume
> other misc setup.
>
> This gets us complete exception coverage of setting up shadow stacks, rather
> than dying with a triple fault.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
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