From: "Roger Pau Monné" <roger.pau@citrix.com>
To: Jan Beulich <jbeulich@suse.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 2/3] x86/smp: use a dedicated scratch cpumask in send_IPI_mask
Date: Thu, 13 Feb 2020 11:03:55 +0100 [thread overview]
Message-ID: <20200213100355.GV4679@Air-de-Roger> (raw)
In-Reply-To: <4849c6bc-e77b-d02f-7d0d-598cbcb3f145@suse.com>
On Thu, Feb 13, 2020 at 10:59:29AM +0100, Jan Beulich wrote:
> On 12.02.2020 17:49, Roger Pau Monne wrote:
> > Using scratch_cpumask in send_IPI_mak is not safe because it can be
> > called from interrupt context, and hence Xen would have to make sure
> > all the users of the scratch cpumask disable interrupts while using
> > it.
> >
> > Instead introduce a new cpumask to be used by send_IPI_mask, and
> > disable interrupts while using.
>
> My first thought here was: What about NMI or #MC context? Even if
> not using the function today (which I didn't check), there shouldn't
> be a latent issue introduced here preventing them from doing so in
> the future. Instead I think you want to allocate the scratch mask
> dynamically (at least if caller context doesn't allow use of the
> generic one), and simply refrain from coalescing IPIs if this
> allocations fails.
Hm, isn't this going to be quite expensive, and hence render the
benefit of using the shorthand moot?
Thanks, Roger.
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next prev parent reply other threads:[~2020-02-13 10:04 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-12 16:49 [Xen-devel] [PATCH 0/3] x86: fixes/improvements for scratch cpumask Roger Pau Monne
2020-02-12 16:49 ` [Xen-devel] [PATCH 1/3] x86/smp: unify header includes in smp.h Roger Pau Monne
2020-02-12 23:05 ` Wei Liu
2020-02-13 9:54 ` Jan Beulich
2020-02-12 16:49 ` [Xen-devel] [PATCH 2/3] x86/smp: use a dedicated scratch cpumask in send_IPI_mask Roger Pau Monne
2020-02-13 9:59 ` Jan Beulich
2020-02-13 10:03 ` Roger Pau Monné [this message]
2020-02-13 10:19 ` Jan Beulich
2020-02-13 11:41 ` Roger Pau Monné
2020-02-13 13:35 ` Jan Beulich
2020-02-12 16:49 ` [Xen-devel] [PATCH 3/3] x86: add accessors for scratch cpu mask Roger Pau Monne
2020-02-13 10:12 ` Jan Beulich
2020-02-13 15:15 ` Roger Pau Monné
2020-02-13 15:43 ` Jan Beulich
2020-02-12 16:53 ` [Xen-devel] [PATCH 0/3] x86: fixes/improvements for scratch cpumask Sander Eikelenboom
2020-02-12 17:01 ` Roger Pau Monné
2020-02-12 17:13 ` Sander Eikelenboom
2020-02-13 9:31 ` Sander Eikelenboom
2020-02-12 21:05 ` Julien Grall
2020-02-13 9:53 ` Jan Beulich
2020-02-13 10:05 ` Roger Pau Monné
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