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Tue, 21 Jul 2020 14:07:00 +0000 (UTC) Date: Tue, 21 Jul 2020 15:06:57 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: "Zhang, Chen" Subject: Re: [PATCH v2 4/4] net/colo: Match is-enabled probe to tracepoint Message-ID: <20200721140657.GI843362@redhat.com> References: <20200717093517.73397-1-r.bolshakov@yadro.com> <20200717093517.73397-5-r.bolshakov@yadro.com> <3f6bcf74d3c348f9b7744305a6343a79@intel.com> MIME-Version: 1.0 In-Reply-To: <3f6bcf74d3c348f9b7744305a6343a79@intel.com> User-Agent: Mutt/1.14.5 (2020-06-23) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.81; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/21 03:39:19 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Li Zhijian , Jason Wang , "qemu-devel@nongnu.org" , Cameron Esfahani , Roman Bolshakov , Stefan Hajnoczi , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Sat, Jul 18, 2020 at 05:58:56PM +0000, Zhang, Chen wrote: > > > > -----Original Message----- > > From: Roman Bolshakov > > Sent: Friday, July 17, 2020 5:35 PM > > To: qemu-devel@nongnu.org > > Cc: Daniel P. Berrangé ; Stefan Hajnoczi > > ; Cameron Esfahani ; Roman > > Bolshakov ; Philippe Mathieu-Daudé > > ; Zhang, Chen ; Li Zhijian > > ; Jason Wang > > Subject: [PATCH v2 4/4] net/colo: Match is-enabled probe to tracepoint > > > > Build of QEMU with dtrace fails on macOS: > > > > LINK x86_64-softmmu/qemu-system-x86_64 > > error: probe colo_compare_miscompare doesn't exist > > error: Could not register probes > > ld: error creating dtrace DOF section for architecture x86_64 > > > > The reason of the error is explained by Adam Leventhal [1]: > > > > Note that is-enabled probes don't have the stability magic so I'm not > > sure how things would work if only is-enabled probes were used. > > > > net/colo code uses is-enabled probes to determine if other probes should be > > used but colo_compare_miscompare itself is not used explicitly. > > Linker doesn't include the symbol and build fails. > > > > The issue can be resolved if is-enabled probe matches the actual trace point > > that is used inside the test. Packet dump toggle is replaced with a compile- > > time conditional definition. > > > > 1. http://markmail.org/message/6grq2ygr5nwdwsnb > > > > Fixes: f4b618360e ("colo-compare: add TCP, UDP, ICMP packet comparison") > > Cc: Philippe Mathieu-Daudé > > Cc: Cameron Esfahani > > Signed-off-by: Roman Bolshakov > > --- > > net/colo-compare.c | 42 ++++++++++++++++++++++-------------------- > > net/filter-rewriter.c | 10 ++++++++-- > > net/trace-events | 2 -- > > 3 files changed, 30 insertions(+), 24 deletions(-) > > (trace_event_get_state_backends(TRACE_COLO_COMPARE_MISCOMPARE)) > > { > > + if (trace_event_get_state_backends(TRACE_COLO_COMPARE_IP_INFO)) > > { > > char pri_ip_src[20], pri_ip_dst[20], sec_ip_src[20], sec_ip_dst[20]; > > > > strcpy(pri_ip_src, inet_ntoa(ppkt->ip->ip_src)); @@ -492,12 +494,12 > > @@ sec: > > g_queue_push_head(&conn->primary_list, ppkt); > > g_queue_push_head(&conn->secondary_list, spkt); > > > > - if > > (trace_event_get_state_backends(TRACE_COLO_COMPARE_MISCOMPARE)) > > { > > - qemu_hexdump((char *)ppkt->data, stderr, > > - "colo-compare ppkt", ppkt->size); > > - qemu_hexdump((char *)spkt->data, stderr, > > - "colo-compare spkt", spkt->size); > > - } > > +#ifdef DEBUG_COLO_PACKETS > > + qemu_hexdump((char *)ppkt->data, stderr, > > + "colo-compare ppkt", ppkt->size); > > + qemu_hexdump((char *)spkt->data, stderr, > > + "colo-compare spkt", spkt->size); #endif > > > > colo_compare_inconsistency_notify(s); > > } > > @@ -533,12 +535,12 @@ static int colo_packet_compare_udp(Packet *spkt, > > Packet *ppkt) > > ppkt->size - offset)) { > > trace_colo_compare_udp_miscompare("primary pkt size", ppkt->size); > > trace_colo_compare_udp_miscompare("Secondary pkt size", spkt- > > >size); > > - if > > (trace_event_get_state_backends(TRACE_COLO_COMPARE_MISCOMPARE)) > > { > > - qemu_hexdump((char *)ppkt->data, stderr, "colo-compare pri pkt", > > - ppkt->size); > > - qemu_hexdump((char *)spkt->data, stderr, "colo-compare sec pkt", > > - spkt->size); > > - } > > +#ifdef DEBUG_COLO_PACKETS > > + qemu_hexdump((char *)ppkt->data, stderr, "colo-compare pri pkt", > > + ppkt->size); > > + qemu_hexdump((char *)spkt->data, stderr, "colo-compare sec pkt", > > + spkt->size); > > +#endif > > Hi Roman, > > I think change the " trace_event_get_state_backends()" to > "trace_colo_compare_main("Dump packet hex: ")" is a better choice here. > It will keep the original code logic and avoid the problem here. That may workaround the immediate bug, but this is still a misuse of the tracing code. Use of any trace point should only trigger actions in the trace infrastructure. If I'm using dtrace backend to monitor events I don't want to see QEMU dumping stuff to stderr. Anything written to stderr is going to trigger disk I/O writing to the VM's logfile, and is also liable to trigger rate limiting which can impact the guest performance. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|