From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Xen-devel <xen-devel@lists.xenproject.org>,
Jan Beulich <JBeulich@suse.com>,
Anthony PERARD <anthony.perard@vates.tech>,
Michal Orzel <michal.orzel@amd.com>,
Julien Grall <julien@xen.org>,
Stefano Stabellini <sstabellini@kernel.org>
Subject: Re: [PATCH v2 5/6] x86/idle: Implement a new MWAIT IPI-elision algorithm
Date: Fri, 4 Jul 2025 19:53:45 +0200 [thread overview]
Message-ID: <aGgVKfbMS8KwX-32@macbook.local> (raw)
In-Reply-To: <20250704163410.1412367-6-andrew.cooper3@citrix.com>
On Fri, Jul 04, 2025 at 05:34:09PM +0100, Andrew Cooper wrote:
> In order elide IPIs, we must be able to identify whether a target CPU is in
> MWAIT at the point it is woken up. i.e. the store to wake it up must also
> identify the state.
>
> Create a new in_mwait variable beside __softirq_pending, so we can use a
> CMPXCHG to set the softirq while also observing the status safely. Implement
> an x86 version of arch_pend_softirq() which does this.
>
> In mwait_idle_with_hints(), advertise in_mwait, with an explanation of
> precisely what it means. X86_BUG_MONITOR can be accounted for simply by not
> advertising in_mwait.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Thanks, Roger.
next prev parent reply other threads:[~2025-07-04 17:53 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-04 16:34 [PATCH v2 0/6] x86/idle: Multiple MWAIT fixes Andrew Cooper
2025-07-04 16:34 ` [PATCH v2 1/6] x86/idle: Remove broken MWAIT implementation Andrew Cooper
2025-07-04 16:34 ` [PATCH v2 2/6] x86/idle: Drop incorrect smp_mb() in mwait_idle_with_hints() Andrew Cooper
2025-07-04 17:51 ` Roger Pau Monné
2025-07-04 16:34 ` [PATCH v2 3/6] x86/idle: Convert force_mwait_ipi_wakeup to X86_BUG_MONITOR Andrew Cooper
2025-07-04 17:52 ` Roger Pau Monné
2025-07-04 16:34 ` [PATCH v2 4/6] xen/softirq: Rework arch_skip_send_event_check() into arch_set_softirq() Andrew Cooper
2025-07-04 16:34 ` [PATCH v2 5/6] x86/idle: Implement a new MWAIT IPI-elision algorithm Andrew Cooper
2025-07-04 17:53 ` Roger Pau Monné [this message]
2025-07-04 16:34 ` [PATCH v2 6/6] x86/idle: Fix buggy "x86/mwait-idle: enable interrupts before C1 on Xeons" Andrew Cooper
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