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 2/3] x86/smp: use a dedicated scratch cpumask in send_IPI_mask
Date: Thu, 13 Feb 2020 10:59:29 +0100 [thread overview]
Message-ID: <4849c6bc-e77b-d02f-7d0d-598cbcb3f145@suse.com> (raw)
In-Reply-To: <20200212164949.56434-3-roger.pau@citrix.com>
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.
Jan
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next prev parent reply other threads:[~2020-02-13 9:59 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 [this message]
2020-02-13 10:03 ` Roger Pau Monné
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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