Re: [Qemu-devel] [PATCH] spapr: Explicitly check machine support before using EVENT_CLASS_HOT_PLUG

From: Thomas Huth <thuth@redhat.com>
To: Greg Kurz <groug@kaod.org>, qemu-devel@nongnu.org
Cc: qemu-ppc@nongnu.org, David Gibson <david@gibson.dropbear.id.au>,
	Peter Maydell <peter.maydell@linaro.org>,
	David Hildenbrand <david@redhat.com>,
	Michael Roth <mdroth@linux.vnet.ibm.com>
Subject: Re: [Qemu-devel] [PATCH] spapr: Explicitly check machine support before using EVENT_CLASS_HOT_PLUG
Date: Fri, 1 Mar 2019 16:24:48 +0100	[thread overview]
Message-ID: <70418309-8593-44be-0549-8531a9ccaa2e@redhat.com> (raw)
In-Reply-To: <155144987334.126105.2493613675615671242.stgit@bahia.lan>

On 01/03/2019 15.17, Greg Kurz wrote:
> 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.
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>
> ---
>  hw/ppc/spapr_events.c |   12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)

Thanks, that fixes the problem for me!

Tested-by: Thomas Huth <thuth@redhat.com>