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Re: [PATCH 4/9] x86/spec-ctrl: Improve all SPEC_CTRL_{ENTER,EXIT}_* comments
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 18 Sep 2023 12:59:05 +0200
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 18 Sep 2023 10:59:20 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 15.09.2023 17:00, Andrew Cooper wrote:
> ... to better explain how they're used.
>
> Doing so highlights that SPEC_CTRL_EXIT_TO_XEN is missing a VERW flush for the
> corner case when e.g. an NMI hits late in an exit-to-guest path.
>
> Leave a TODO, which will be addressed in subsequent patches which arrange for
> DO_COND_VERW to be safe within SPEC_CTRL_EXIT_TO_XEN.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Two nits though:
> @@ -233,7 +236,11 @@
> X86_FEATURE_SC_MSR_PV
> .endm
>
> -/* Use in interrupt/exception context. May interrupt Xen or PV context. */
> +/*
> + * Used after an exception or maskable interrupt, hitting Xen or PV context.
> + * There will either be a guest speculation context, or (baring fatal
Isn't this "barring"?
> @@ -260,7 +270,13 @@
> .endm
>
> /*
> - * Use in IST interrupt/exception context. May interrupt Xen or PV context.
> + * Used after an IST entry hitting Xen or PV context. Special care is
> needed,
> + * because when hitting Xen context, there may not a well-formed speculation
Missing "be"?
Jan
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