From: Jan Beulich <jbeulich@suse.com>
To: Roger Pau Monne <roger.pau@citrix.com>
Cc: xen-devel@lists.xenproject.org,
Sander Eikelenboom <linux@eikelenboom.it>, Wei Liu <wl@xen.org>,
Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [Xen-devel] [PATCH v5 4/4] x86/smp: do not use scratch_cpumask when in interrupt or exception context
Date: Wed, 26 Feb 2020 14:10:44 +0100 [thread overview]
Message-ID: <3cea2d54-345b-d632-2d2f-320fe586e0ea@suse.com> (raw)
In-Reply-To: <20200226123844.29519-1-roger.pau@citrix.com>
On 26.02.2020 13:38, Roger Pau Monne wrote:
> Using scratch_cpumask in send_IPI_mask is not safe in IRQ or exception
> context because it can nest, and hence send_IPI_mask could be
> overwriting another user scratch cpumask data when used in such
> contexts.
>
> Instead introduce a new cpumask to be used by send_IPI_mask, and
> disable interrupts while using it.
With this now apparently stale sentence dropped (easily done
while committing)
> Fallback to not using the scratch cpumask (and hence not attemping to
> optimize IPI sending by using a shorthand) when in IRQ or exception
> context. Note that the scratch cpumask cannot be used when
> non-maskable interrupts are being serviced (NMI or #MC) and hence
> fallback to not using the shorthand in that case, like it was done
> previously.
>
> Fixes: 5500d265a2a8 ('x86/smp: use APIC ALLBUT destination shorthand when possible')
> Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Jan
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next prev parent reply other threads:[~2020-02-26 13:10 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 12:19 [Xen-devel] [PATCH v4 0/4] x86/smp: fix send_IPI_mask usage of scratch_cpumask Roger Pau Monne
2020-02-26 12:19 ` [Xen-devel] [PATCH v4 1/4] x86: introduce a nmi_count tracking variable Roger Pau Monne
2020-02-26 13:00 ` Jan Beulich
2020-02-26 12:19 ` [Xen-devel] [PATCH v4 2/4] x86: track when in NMI context Roger Pau Monne
2020-02-26 13:02 ` Jan Beulich
2020-02-26 12:19 ` [Xen-devel] [PATCH v4 3/4] x86: track when in #MC context Roger Pau Monne
2020-02-26 13:09 ` Jan Beulich
2020-02-26 12:19 ` [Xen-devel] [PATCH v4 4/4] x86/smp: do not use scratch_cpumask when in interrupt or exception context Roger Pau Monne
2020-02-26 12:27 ` Roger Pau Monné
2020-02-26 12:38 ` [Xen-devel] [PATCH v5 " Roger Pau Monne
2020-02-26 13:10 ` Jan Beulich [this message]
2020-02-26 14:02 ` Roger Pau Monné
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