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Mon, 23 Aug 2021 15:33:19 +0200 (CEST) From: Markus Armbruster To: Daniel Henrique Barboza Subject: Re: [PATCH for-6.2 v6 6/7] spapr: use DEVICE_UNPLUG_ERROR to report unplug errors References: <20210719200827.1507276-1-danielhb413@gmail.com> <20210719200827.1507276-7-danielhb413@gmail.com> <87a6ltbb7w.fsf@dusky.pond.sub.org> Date: Mon, 23 Aug 2021 15:33:19 +0200 In-Reply-To: (Daniel Henrique Barboza's message of "Mon, 9 Aug 2021 15:47:14 -0300") Message-ID: <87pmu4cmlc.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=216.205.24.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.743, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: groug@kaod.org, qemu-ppc@nongnu.org, qemu-devel@nongnu.org, david@gibson.dropbear.id.au Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Daniel Henrique Barboza writes: > On 8/7/21 11:06 AM, Markus Armbruster wrote: >> Daniel Henrique Barboza writes: >> >>> Linux Kernel 5.12 is now unisolating CPU DRCs in the device_removal >>> error path, signalling that the hotunplug process wasn't successful. >>> This allow us to send a DEVICE_UNPLUG_ERROR in drc_unisolate_logical() >>> to signal this error to the management layer. >>> >>> We also have another error path in spapr_memory_unplug_rollback() for >>> configured LMB DRCs. Kernels older than 5.13 will not unisolate the LMBs >>> in the hotunplug error path, but it will reconfigure them. Let's send >>> the DEVICE_UNPLUG_ERROR event in that code path as well to cover the >>> case of older kernels. >>> >>> Reviewed-by: Greg Kurz >>> Signed-off-by: Daniel Henrique Barboza >>> --- >>> hw/ppc/spapr.c | 9 ++++++++- >>> hw/ppc/spapr_drc.c | 18 ++++++++++++------ >>> 2 files changed, 20 insertions(+), 7 deletions(-) >>> >>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c >>> index 1611d7ab05..5459f9a7e9 100644 >>> --- a/hw/ppc/spapr.c >>> +++ b/hw/ppc/spapr.c >>> @@ -29,6 +29,7 @@ >>> #include "qemu/datadir.h" >>> #include "qapi/error.h" >>> #include "qapi/qapi-events-machine.h" >>> +#include "qapi/qapi-events-qdev.h" >>> #include "qapi/visitor.h" >>> #include "sysemu/sysemu.h" >>> #include "sysemu/hostmem.h" >>> @@ -3686,13 +3687,19 @@ void spapr_memory_unplug_rollback(SpaprMachineState *spapr, DeviceState *dev) >>> /* >>> * Tell QAPI that something happened and the memory >>> - * hotunplug wasn't successful. >>> + * hotunplug wasn't successful. Keep sending >>> + * MEM_UNPLUG_ERROR even while sending DEVICE_UNPLUG_ERROR >>> + * until the deprecation MEM_UNPLUG_ERROR is due. >>> */ >>> if (dev->id) { >>> qapi_error = g_strdup_printf("Memory hotunplug rejected by the guest " >>> "for device %s", dev->id); >>> qapi_event_send_mem_unplug_error(dev->id, qapi_error); >>> } >>> + >>> + qapi_event_send_device_unplug_error(!!dev->id, dev->id, >>> + dev->canonical_path, >>> + qapi_error != NULL, qapi_error); >>> } >>> >> When dev->id is null, we send something like >> >> {"event": "DEVICE_UNPLUG_ERROR", >> "data": {"path": "/machine/..."}, >> "timestamp": ...} >> >> Unless I'm missing something, this is all the information the management >> application really needs. >> >> When dev->id is non-null, we add to "data": >> >> "device": "dev123", >> "msg": "Memory hotunplug rejected by the guest for device dev123", >> >> I'm fine with emitting the device ID when we have it. >> >> What's the intended use of "msg"? >> >> Could DEVICE_UNPLUG_ERROR ever be emitted for this device with a >> different "msg"? > > > It won't have a different 'msg' for the current use of the event in both ppc64 > and x86. It'll always be the same ' hotunplug rejected by the guest' > message. > > The idea is that a future caller might want to insert a more informative > message, such as "hotunplug failed: memory is being used by kernel space" > or any other more specific condition. But then I guess we can argue that, > if that time comes, one can just add this new optional 'msg' member in this > event, and for now we can live without it. > > Would you oppose to renaming this new event to "DEVICE_UNPLUG_GUEST_ERROR" > and then remove the 'msg' member? I guess this rename would make it clearer > for management that we're reporting a guest side error, making any further > clarifications via 'msg' unneeded. No objection.