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Message-ID: <ZIzM13q+zI7d1eZs@araj-dh-work>
Date: Fri, 16 Jun 2023 13:57:59 -0700
From: Ashok Raj <ashok.raj@...el.com>
To: Thomas Gleixner <tglx@...utronix.de>
CC: LKML <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
Mario Limonciello <mario.limonciello@....com>,
Tom Lendacky <thomas.lendacky@....com>,
"Tony Battersby" <tonyb@...ernetics.com>,
Ashok Raj <ashok.raj@...ux.intel.com>,
Tony Luck <tony.luck@...el.com>,
Arjan van de Veen <arjan@...ux.intel.com>,
Eric Biederman <ebiederm@...ssion.com>,
Ashok Raj <ashok.raj@...el.com>
Subject: Re: [patch v3 1/7] x86/smp: Make stop_other_cpus() more robust
On Fri, Jun 16, 2023 at 08:01:56PM +0200, Thomas Gleixner wrote:
> On Fri, Jun 16 2023 at 07:13, Ashok Raj wrote:
> > On Fri, Jun 16, 2023 at 09:53:25AM +0200, Thomas Gleixner wrote:
> >> > can we simplify this by just apic->send_IPI(cpu, NMI_VECTOR); ??
> >>
> >> That would not set APIC_DM_NMI in delivery mode and the IPI would be
> >> sent with APIC_DM_FIXED.
> >
> > That's correct.
> >
> > Maybe if we use apic->send_IPI_mask(cpumask_of(cpu), NMI_VECTOR)
> >
> > apic->send_IPI_mask(cpumask_of(cpu),NMI_VECTOR)
> > __x2apic_send_IPI_mask()
> > __x2apic_send_IPI_dest()
> > unsigned long cfg = __prepare_ICR(0, vector, dest);
> > native_x2apic_icr_write(cfg, apicid);
> >
> > __prepare_ICR() seems to have the magic for APIC_DM_NMI?
>
> Bah. I clearly neither can read nor can remember any of the internals of
> that code:
>
> apic->send_IPI()
> x2apic_send_IPI()
> __x2apic_send_IPI_dest()
>
> It also works for all other APIC incarnations.
Works!
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