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Re: [PATCH 1/5] x86/mwait-idle: mention assumption that WBINVD is not needed
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Tue, 18 Jan 2022 11:18:32 +0100
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Mon, Sep 06, 2021 at 02:59:46PM +0200, Jan Beulich wrote:
> From: Alexander Monakov <amonakov@xxxxxxxxx>
>
> Intel SDM does not explicitly say that entering a C-state via MWAIT will
> implicitly flush CPU caches as appropriate for that C-state. However,
> documentation for individual Intel CPU generations does mention this
> behavior.
>
> Since intel_idle binds to any Intel CPU with MWAIT, list this assumption
> of MWAIT behavior.
>
> In passing, reword opening comment to make it clear that the driver can
> load on any old and future Intel CPU with MWAIT.
>
> Signed-off-by: Alexander Monakov <amonakov@xxxxxxxxx>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> [Linux commit: 8bb2e2a887afdf8a39e68fa0dccf82a168aae655]
>
> Dropped "reword opending comment" part - this doesn't apply to our code:
> First thing mwait_idle_probe() does is call x86_match_cpu(); we do not
> have a 2nd such call looking for just MWAIT (in order to the use _CST
> data directly, which we can't get our hands at _CST at this point yet).
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Thanks, Roger.
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