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Re: [PATCH 1/3] x86/spec-ctrl: Consistently halt speculation using int3
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 19 Jul 2022 08:13:42 +0200
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 19 Jul 2022 06:14:00 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 18.07.2022 22:50, Andrew Cooper wrote:
> The RSB stuffing loop and retpoline thunks date from the very beginning, when
> halting speculation was a brand new field.
>
> These days, we've largely settled on int3 for halting speculation in
> non-architectural paths. It's a single byte, and is fully serialising - a
> requirement for delivering #BP if it were to execute.
>
> Update the thunks. Mostly for consistency across the codebase, but it does
> shrink every entrypath in Xen by 6 bytes which is a marginal win.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
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