From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:45038) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gzlwe-0001Cw-Dn for qemu-devel@nongnu.org; Fri, 01 Mar 2019 12:27:37 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gzlwc-0007Y9-DT for qemu-devel@nongnu.org; Fri, 01 Mar 2019 12:27:36 -0500 Received: from 7.mo179.mail-out.ovh.net ([46.105.61.94]:43094) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gzlwa-0007Tw-Bj for qemu-devel@nongnu.org; Fri, 01 Mar 2019 12:27:34 -0500 Received: from player735.ha.ovh.net (unknown [10.109.159.90]) by mo179.mail-out.ovh.net (Postfix) with ESMTP id 4968D113643 for ; Fri, 1 Mar 2019 18:27:27 +0100 (CET) Date: Fri, 1 Mar 2019 18:27:17 +0100 From: Greg Kurz Message-ID: <20190301182717.2d67d621@bahia.lan> In-Reply-To: <155145721677.30057.3700488922747499209@sif> References: <155144987334.126105.2493613675615671242.stgit@bahia.lan> <155145721677.30057.3700488922747499209@sif> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] spapr: Explicitly check machine support before using EVENT_CLASS_HOT_PLUG List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Michael Roth Cc: qemu-devel@nongnu.org, Peter Maydell , Thomas Huth , David Hildenbrand , qemu-ppc@nongnu.org, David Gibson On Fri, 01 Mar 2019 10:20:16 -0600 Michael Roth wrote: > Quoting Greg Kurz (2019-03-01 08:17:53) > > Recent commit b8165118f52c "spapr: support memory unplug for qtest" broke > > CPU hotplug tests for old machine types: > > > > $ QTEST_QEMU_BINARY=ppc64-softmmu/qemu-system-ppc64 ./tests/cpu-plug-test -m=slow > > /ppc64/cpu-plug/pseries-3.1/device-add/2x3x1&maxcpus=6: OK > > /ppc64/cpu-plug/pseries-2.12-sxxm/device-add/2x3x1&maxcpus=6: OK > > /ppc64/cpu-plug/pseries-3.0/device-add/2x3x1&maxcpus=6: OK > > /ppc64/cpu-plug/pseries-2.10/device-add/2x3x1&maxcpus=6: OK > > /ppc64/cpu-plug/pseries-2.11/device-add/2x3x1&maxcpus=6: OK > > /ppc64/cpu-plug/pseries-2.12/device-add/2x3x1&maxcpus=6: OK > > /ppc64/cpu-plug/pseries-2.9/device-add/2x3x1&maxcpus=6: OK > > /ppc64/cpu-plug/pseries-2.7/device-add/2x3x1&maxcpus=6: ** > > ERROR:/home/thuth/devel/qemu/hw/ppc/spapr_events.c:313:rtas_event_log_to_source: assertion failed: (source->enabled) > > Broken pipe > > /home/thuth/devel/qemu/tests/libqtest.c:143: kill_qemu() detected QEMU death from signal 6 (Aborted) (core dumped) > > Aborted (core dumped) > > > > The rtas_event_log_to_source() function is supposed to return the event > > source to be used for a given event type. In the case of hotplug, it first > > tries EVENT_CLASS_HOT_PLUG and, if the guest doesn't support it, it falls > > back to EVENT_CLASS_EPOW. > > > > This works well for machine types that enable EVENT_CLASS_HOT_PLUG. For > > older machine types, this happened to work because they don't set the > > OV5_HP_EVT bit in spapr->ov5. CAS hence logically keeps the bit cleared > > in spapr->ov5_cas and we avoid the assert. > > > > As shown by commit b8165118f52c, the logic is fragile and we need a > > bigger hammer to ensure that rtas_event_log_to_source() doesn't go > > down the EVENT_CLASS_HOT_PLUG path with older machine types. > > I think that fact that we set spapr->ov5 based on relevant machine > options/support being there, and the fact that this means they won't > show up in ov5_cas, is a nice thing to assert and rely on, since being > able to rely on that keeps keeps the logic throughout the code tied to > ov5/ov5_cas and avoids the need to keep re-checking things like > spapr->use_hotplug_event_source (and various other options tied to an > OV5 capability) after init time. > True. > I think this particular case is purely the result of us violating (via > b8165118f52c) the condition that bits that aren't ever set in spapr->ov5 > should never end up in spapr->ov5_cas, and losing that precondition might > make the code harder to reason about since now we have to check both > ov5_cas and the related options (rather than 1 necessarilly following > from the other). > > Another approach might be to revert b8165118f52c, and then add a hook for > qtest_enabled() that does a fake CAS negotiation (which I guess would > essentially involve copying spapr->ov5 into spapr->ov5_cas). This would > maintain the flow of machine options -> spapr->ov5 -> spapr->ov5_cas and > still let qtest do it's thing (AFAICT). > Yeah, that looks nice. I'll try that right away. > > > > Signed-off-by: Greg Kurz > > --- > > hw/ppc/spapr_events.c | 12 +++++++----- > > 1 file changed, 7 insertions(+), 5 deletions(-) > > > > diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c > > index ab9a1f0063d5..1a09dab6857d 100644 > > --- a/hw/ppc/spapr_events.c > > +++ b/hw/ppc/spapr_events.c > > @@ -307,11 +307,13 @@ rtas_event_log_to_source(sPAPRMachineState *spapr, int log_type) > > > > switch (log_type) { > > case RTAS_LOG_TYPE_HOTPLUG: > > - source = spapr_event_sources_get_source(spapr->event_sources, > > - EVENT_CLASS_HOT_PLUG); > > - if (spapr_ovec_test(spapr->ov5_cas, OV5_HP_EVT)) { > > - g_assert(source->enabled); > > - break; > > + if (spapr->use_hotplug_event_source) { > > + source = spapr_event_sources_get_source(spapr->event_sources, > > + EVENT_CLASS_HOT_PLUG); > > + if (spapr_ovec_test(spapr->ov5_cas, OV5_HP_EVT)) { > > + g_assert(source->enabled); > > + break; > > + } > > } > > /* fall back to epow for legacy hotplug interrupt source */ > > case RTAS_LOG_TYPE_EPOW: > > > >