From: Jan Beulich <jbeulich@suse.com>
To: Julien Grall <julien@xen.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
George Dunlap <George.Dunlap@eu.citrix.com>,
Ian Jackson <iwj@xenproject.org>, Wei Liu <wl@xen.org>,
Stefano Stabellini <sstabellini@kernel.org>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH v2 6/8] evtchn: convert vIRQ lock to an r/w one
Date: Fri, 30 Oct 2020 13:00:15 +0100 [thread overview]
Message-ID: <33ff45e9-d869-9262-29e0-fa66e3ffb726@suse.com> (raw)
In-Reply-To: <6dec1d48-b8c8-6122-087c-38f36f30596e@xen.org>
On 30.10.2020 11:57, Julien Grall wrote:
> On 20/10/2020 15:10, Jan Beulich wrote:
>> --- a/xen/common/event_channel.c
>> +++ b/xen/common/event_channel.c
>> @@ -449,6 +449,13 @@ int evtchn_bind_virq(evtchn_bind_virq_t
>>
>> spin_unlock_irqrestore(&chn->lock, flags);
>>
>> + /*
>> + * If by any, the update of virq_to_evtchn[] would need guarding by
>> + * virq_lock, but since this is the last action here, there's no strict
>> + * need to acquire the lock. Hnece holding event_lock isn't helpful
>
> s/Hnece/Hence/
>
>> + * anymore at this point, but utilize that its unlocking acts as the
>> + * otherwise necessary smp_wmb() here.
>> + */
>> v->virq_to_evtchn[virq] = bind->port = port;
>
> I think all access to v->virq_to_evtchn[virq] should use ACCESS_ONCE()
> or {read, write}_atomic() to avoid any store/load tearing.
IOW you're suggesting this to be the subject of a separate patch?
I don't think such a conversion belongs here (nor even in this
series, seeing the much wider applicability of such a change
throughout the code base). Or are you seeing anything here which
would require such a conversion to be done as a prereq?
Jan
next prev parent reply other threads:[~2020-10-30 12:00 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-20 14:06 [PATCH v2 0/8] evtchn: recent XSAs follow-on Jan Beulich
2020-10-20 14:08 ` [PATCH v2 1/8] evtchn: avoid race in get_xen_consumer() Jan Beulich
2020-10-21 15:46 ` Roger Pau Monné
2020-10-22 7:33 ` Jan Beulich
2020-10-22 8:11 ` Roger Pau Monné
2020-10-22 8:15 ` Jan Beulich
2020-10-22 8:29 ` Roger Pau Monné
2020-10-22 8:56 ` Jan Beulich
2020-10-22 9:25 ` Roger Pau Monné
2020-10-22 9:21 ` Roger Pau Monné
2020-10-30 10:15 ` Julien Grall
2020-10-20 14:08 ` [PATCH v2 2/8] evtchn: replace FIFO-specific header by generic private one Jan Beulich
2020-10-21 16:00 ` Roger Pau Monné
2020-10-30 10:21 ` Julien Grall
2020-10-30 10:42 ` Jan Beulich
2020-10-30 10:44 ` Julien Grall
2020-10-20 14:09 ` [PATCH v2 3/8] evtchn: rename and adjust guest_enabled_event() Jan Beulich
2020-10-22 10:28 ` Roger Pau Monné
2020-10-20 14:09 ` [PATCH v2 4/8] evtchn: let evtchn_set_priority() acquire the per-channel lock Jan Beulich
2020-10-22 11:17 ` Roger Pau Monné
2020-10-22 13:34 ` Jan Beulich
2020-10-20 14:10 ` [PATCH v2 5/8] evtchn: drop acquiring of per-channel lock from send_guest_{global,vcpu}_virq() Jan Beulich
2020-10-22 16:00 ` Roger Pau Monné
2020-10-22 16:17 ` Jan Beulich
2020-10-30 10:38 ` Julien Grall
2020-10-30 10:49 ` Jan Beulich
2020-10-30 10:57 ` Julien Grall
2020-10-30 11:15 ` Jürgen Groß
2020-10-30 11:55 ` Jan Beulich
2020-10-30 12:27 ` Jürgen Groß
2020-10-30 12:52 ` Jan Beulich
2020-10-30 13:02 ` Jürgen Groß
2020-10-30 13:38 ` Jan Beulich
2020-10-30 13:43 ` Jürgen Groß
2020-10-20 14:10 ` [PATCH v2 6/8] evtchn: convert vIRQ lock to an r/w one Jan Beulich
2020-10-30 10:57 ` Julien Grall
2020-10-30 12:00 ` Jan Beulich [this message]
2020-10-30 12:08 ` Julien Grall
2020-10-30 12:25 ` Jan Beulich
2020-10-30 12:46 ` Julien Grall
2020-10-20 14:11 ` [PATCH v2 7/8] evtchn: convert domain event " Jan Beulich
2020-10-20 14:13 ` [PATCH RFC v2 8/8] evtchn: don't call Xen consumer callback with per-channel lock held Jan Beulich
2020-11-03 10:17 ` Isaila Alexandru
2020-11-03 14:54 ` Tamas K Lengyel
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