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[184.144.111.238]) by smtp.gmail.com with ESMTPSA id f24sm262540qtq.82.2021.07.16.07.18.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Jul 2021 07:18:44 -0700 (PDT) Date: Fri, 16 Jul 2021 10:18:43 -0400 From: Peter Xu To: Thanos Makatos Subject: Re: Question on memory commit during MR finalize() Message-ID: References: <20200420210049.GA420399@xz-x1> <20200420233115.GB420399@xz-x1> <5ed295a3-9e4a-0dca-adc6-5361dc78a83c@redhat.com> <20200421104334.GC420399@xz-x1> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=216.205.24.124; envelope-from=peterx@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=-0.7, 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_H4=0.001, RCVD_IN_MSPIKE_WL=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: Paolo Bonzini , John Levon , John G Johnson , Markus Armbruster , QEMU Devel Mailing List Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Jul 16, 2021 at 11:42:02AM +0000, Thanos Makatos wrote: > > -----Original Message----- > > From: Peter Xu > > Sent: 15 July 2021 19:35 > > To: Thanos Makatos > > Cc: Paolo Bonzini ; Markus Armbruster > > ; QEMU Devel Mailing List > devel@nongnu.org>; John Levon ; John G > > Johnson > > Subject: Re: Question on memory commit during MR finalize() > >=20 > > On Thu, Jul 15, 2021 at 02:27:48PM +0000, Thanos Makatos wrote: > > > Hi Peter, > >=20 > > Hi, Thanos, > >=20 > > > We're hitting this issue using a QEMU branch where JJ is using vfio-u= ser as > > the transport for multiprocess-qemu > > (https://urldefense.proofpoint.com/v2/url?u=3Dhttps- > > 3A__github.com_oracle_qemu_issues_9&d=3DDwIBaQ&c=3Ds883GpUCOChKOHi > > ocYtGcg&r=3DXTpYsh5Ps2zJvtw6ogtti46atk736SI4vgsJiUKIyDE&m=3D9nFuGF9kg5l > > ZsKPi03BNzo9pckG8DlodVG0LuEofnKw&s=3Ddcp70CIgJljcWFwSRZm5zZRJj80jX > > XERLwpbH6ZcgzQ&e=3D ). We can reproduce it fairly reliably by migrating= a > > virtual SPDK NVMe controller (the NVMf/vfio-user target with experiment= al > > migration support, https://urldefense.proofpoint.com/v2/url?u=3Dhttps- > > 3A__review.spdk.io_gerrit_c_spdk_spdk_- > > 2B_7617_14&d=3DDwIBaQ&c=3Ds883GpUCOChKOHiocYtGcg&r=3DXTpYsh5Ps2zJvtw > > 6ogtti46atk736SI4vgsJiUKIyDE&m=3D9nFuGF9kg5lZsKPi03BNzo9pckG8DlodVG0 > > LuEofnKw&s=3DiXolOQM5sYj4IB-cf__Ta8jgKXZqisYE-uuwq6qnbLo&e=3D ). I can > > provide detailed repro instructions but first I want to make sure we're= not > > missing any patches. > >=20 > > I don't think you missed any bug fix patches, as the issue I mentioned = can > > only be trigger with my own branch at that time, and that's fixed when = my > > patchset got merged. > >=20 > > However if you encountered the same issue, it's possible that there's a= n > > incorrect use of qemu memory/cpu API too somewhere there so similar > > issue is triggered. For example, in my case it was run_on_cpu() called > > incorrectly within memory layout changing so BQL is released without be= ing > > noticed. > >=20 > > I've got a series that tries to expose these hard to debug issues: > >=20 > > https://urldefense.proofpoint.com/v2/url?u=3Dhttps- > > 3A__lore.kernel.org_qemu-2Ddevel_20200421162108.594796-2D1-2Dpeterx- > > 40redhat.com_&d=3DDwIBaQ&c=3Ds883GpUCOChKOHiocYtGcg&r=3DXTpYsh5Ps2zJ > > vtw6ogtti46atk736SI4vgsJiUKIyDE&m=3D9nFuGF9kg5lZsKPi03BNzo9pckG8Dlod > > VG0LuEofnKw&s=3DkQRJEb4CQmxEirS-III15QJz_phzhCYLIgjOF-SB9Pk&e=3D > >=20 > > Obviously the series didn't track enough interest so it didn't get merg= ed. > > However maybe that's also something useful to what you're debugging, so > > you can apply those patches onto your branch and see the stack when it > > reproduces again. Logically with these sanity patches it could fail ear= lier than > > what you've hit right now (which I believe should be within the RCU thr= ead; > > btw it would be interesting to share your stack too when it's hit) and = it could > > provide more useful information. > >=20 > > I saw that the old series won't apply onto master any more, so I rebase= d it > > and pushed it here (with one patch dropped since someone wrote a simila= r > > patch and got merged, so there're only 7 patches in the new tree): > >=20 > > https://urldefense.proofpoint.com/v2/url?u=3Dhttps- > > 3A__github.com_xzpeter_qemu_tree_memory- > > 2Dsanity&d=3DDwIBaQ&c=3Ds883GpUCOChKOHiocYtGcg&r=3DXTpYsh5Ps2zJvtw6og > > tti46atk736SI4vgsJiUKIyDE&m=3D9nFuGF9kg5lZsKPi03BNzo9pckG8DlodVG0LuE > > ofnKw&s=3DG-8FV-H-VcZTgCVRfTEVKo1GALIk2PqBvTdAcAXFoZ0&e=3D > >=20 > > No guarantee it'll help, but IMHO worth trying. >=20 > The memory-sanity branch fails to build: >=20 > ./configure --prefix=3D/opt/qemu-xzpeter --target-list=3Dx86_64-linux-use= r --enable-debug > make -j 8 > ... > [697/973] Linking target qemu-x86_64 > FAILED: qemu-x86_64 > c++ -o qemu-x86_64 libcommon.fa.p/cpus-common.c.o libcommon.fa.p/page-va= ry-common.c.o libcommon.fa.p/disas_i386.c.o libcommon.fa.p/disas_capstone.c= .o libcommon.fa.p/hw_core_cpu-common.c.o libcommon.fa.p/ebpf_ebpf_rss-stub.= c.o libcommon.fa.p/accel_accel-user.c.o libqemu-x86_64-linux-user.fa.p/targ= et_i386_tcg_user_excp_helper.c.o libqemu-x86_64-linux-user.fa.p/target_i386= _tcg_user_seg_helper.c.o libqemu-x86_64-linux-user.fa.p/linux-user_x86_64_s= ignal.c.o libqemu-x86_64-linux-user.fa.p/linux-user_x86_64_cpu_loop.c.o lib= qemu-x86_64-linux-user.fa.p/target_i386_cpu.c.o libqemu-x86_64-linux-user.f= a.p/target_i386_gdbstub.c.o libqemu-x86_64-linux-user.fa.p/target_i386_help= er.c.o libqemu-x86_64-linux-user.fa.p/target_i386_xsave_helper.c.o libqemu-= x86_64-linux-user.fa.p/target_i386_cpu-dump.c.o libqemu-x86_64-linux-user.f= a.p/target_i386_sev-stub.c.o libqemu-x86_64-linux-user.fa.p/target_i386_kvm= _kvm-stub.c.o libqemu-x86_64-linux-user.fa.p/target_i386_tcg_bpt_helper.c.o= libqemu-x86_64-linux-user.fa.p/target_i386_tcg_cc_helper.c.o libqemu-x86_6= 4-linux-user.fa.p/target_i386_tcg_excp_helper.c.o libqemu-x86_64-linux-user= .fa.p/target_i386_tcg_fpu_helper.c.o libqemu-x86_64-linux-user.fa.p/target_= i386_tcg_int_helper.c.o libqemu-x86_64-linux-user.fa.p/target_i386_tcg_mem_= helper.c.o libqemu-x86_64-linux-user.fa.p/target_i386_tcg_misc_helper.c.o l= ibqemu-x86_64-linux-user.fa.p/target_i386_tcg_mpx_helper.c.o libqemu-x86_64= -linux-user.fa.p/target_i386_tcg_seg_helper.c.o libqemu-x86_64-linux-user.f= a.p/target_i386_tcg_tcg-cpu.c.o libqemu-x86_64-linux-user.fa.p/target_i386_= tcg_translate.c.o libqemu-x86_64-linux-user.fa.p/trace_control-target.c.o l= ibqemu-x86_64-linux-user.fa.p/cpu.c.o libqemu-x86_64-linux-user.fa.p/disas.= c.o libqemu-x86_64-linux-user.fa.p/gdbstub.c.o libqemu-x86_64-linux-user.fa= .p/page-vary.c.o libqemu-x86_64-linux-user.fa.p/tcg_optimize.c.o libqemu-x8= 6_64-linux-user.fa.p/tcg_region.c.o libqemu-x86_64-linux-user.fa.p/tcg_tcg.= c.o libqemu-x86_64-linux-user.fa.p/tcg_tcg-common.c.o libqemu-x86_64-linux-= user.fa.p/tcg_tcg-op.c.o libqemu-x86_64-linux-user.fa.p/tcg_tcg-op-gvec.c.o= libqemu-x86_64-linux-user.fa.p/tcg_tcg-op-vec.c.o libqemu-x86_64-linux-use= r.fa.p/fpu_softfloat.c.o libqemu-x86_64-linux-user.fa.p/accel_accel-common.= c.o libqemu-x86_64-linux-user.fa.p/accel_tcg_tcg-all.c.o libqemu-x86_64-lin= ux-user.fa.p/accel_tcg_cpu-exec-common.c.o libqemu-x86_64-linux-user.fa.p/a= ccel_tcg_cpu-exec.c.o libqemu-x86_64-linux-user.fa.p/accel_tcg_tcg-runtime-= gvec.c.o libqemu-x86_64-linux-user.fa.p/accel_tcg_tcg-runtime.c.o libqemu-x= 86_64-linux-user.fa.p/accel_tcg_translate-all.c.o libqemu-x86_64-linux-user= .fa.p/accel_tcg_translator.c.o libqemu-x86_64-linux-user.fa.p/accel_tcg_use= r-exec.c.o libqemu-x86_64-linux-user.fa.p/accel_tcg_user-exec-stub.c.o libq= emu-x86_64-linux-user.fa.p/accel_tcg_plugin-gen.c.o libqemu-x86_64-linux-us= er.fa.p/accel_stubs_hax-stub.c.o libqemu-x86_64-linux-user.fa.p/accel_stubs= _xen-stub.c.o libqemu-x86_64-linux-user.fa.p/accel_stubs_kvm-stub.c.o libqe= mu-x86_64-linux-user.fa.p/plugins_loader.c.o libqemu-x86_64-linux-user.fa.p= /plugins_core.c.o libqemu-x86_64-linux-user.fa.p/plugins_api.c.o libqemu-x8= 6_64-linux-user.fa.p/linux-user_elfload.c.o libqemu-x86_64-linux-user.fa.p/= linux-user_exit.c.o libqemu-x86_64-linux-user.fa.p/linux-user_fd-trans.c.o = libqemu-x86_64-linux-user.fa.p/linux-user_linuxload.c.o libqemu-x86_64-linu= x-user.fa.p/linux-user_main.c.o libqemu-x86_64-linux-user.fa.p/linux-user_m= map.c.o libqemu-x86_64-linux-user.fa.p/linux-user_safe-syscall.S.o libqemu-= x86_64-linux-user.fa.p/linux-user_signal.c.o libqemu-x86_64-linux-user.fa.p= /linux-user_strace.c.o libqemu-x86_64-linux-user.fa.p/linux-user_syscall.c.= o libqemu-x86_64-linux-user.fa.p/linux-user_uaccess.c.o libqemu-x86_64-linu= x-user.fa.p/linux-user_uname.c.o libqemu-x86_64-linux-user.fa.p/thunk.c.o l= ibqemu-x86_64-linux-user.fa.p/meson-generated_.._x86_64-linux-user-gdbstub-= xml.c.o libqemu-x86_64-linux-user.fa.p/meson-generated_.._trace_generated-h= elpers.c.o -Wl,--as-needed -Wl,--no-undefined -pie -Wl,--whole-archive libh= wcore.fa libqom.fa -Wl,--no-whole-archive -Wl,--warn-common -Wl,-z,relro -W= l,-z,now -m64 -fstack-protector-strong -Wl,--start-group libcapstone.a libq= emuutil.a libhwcore.fa libqom.fa -ldl -Wl,--dynamic-list=3D/root/src/qemu/b= uild/qemu-plugins-ld.symbols -lrt -lutil -lm -pthread -Wl,--export-dynamic = -lgmodule-2.0 -lglib-2.0 -lstdc++ -Wl,--end-group > /usr/bin/ld: libcommon.fa.p/cpus-common.c.o: in function `do_run_on_cpu': > /root/src/qemu/build/../cpus-common.c:153: undefined reference to `qemu_c= ond_wait_iothread' > collect2: error: ld returned 1 exit status > [698/973] Compiling C object tests/fp/libsoftfloat.a.p/berkeley-softfloat= -3_source_f32_to_ui64_r_minMag.c.o > [699/973] Compiling C object tests/fp/libsoftfloat.a.p/berkeley-softfloat= -3_source_f32_to_i32_r_minMag.c.o > [700/973] Compiling C object tests/fp/libsoftfloat.a.p/berkeley-softfloat= -3_source_f32_to_f16.c.o > [701/973] Compiling C object tests/fp/libsoftfloat.a.p/berkeley-softfloat= -3_source_f32_to_f64.c.o > [702/973] Compiling C object tests/fp/libsoftfloat.a.p/berkeley-softfloat= -3_source_f32_to_i64_r_minMag.c.o > [703/973] Compiling C object tests/fp/libsoftfloat.a.p/berkeley-softfloat= -3_source_f32_to_extF80M.c.o > [704/973] Compiling C object tests/fp/libsoftfloat.a.p/berkeley-softfloat= -3_source_f32_to_extF80.c.o > ninja: build stopped: subcommand failed. > make[1]: *** [Makefile:154: run-ninja] Error 1 > make[1]: Leaving directory '/root/src/qemu/build' > make: *** [GNUmakefile:11: all] Error 2 So it fails linux-user... I can fix the compilation, but it should pass x86_64-softmmu. More importantly - are you using linux-user binaries? The thing is my branch will only be helpful to debug BQL related issues, so if that's the case then please ignore the branch as linux-user shouldn't be us= ing bql, then my branch won't help. >=20 > Regarding the stack trace, I can very easily reproduce it on our branch, = I know exactly where to set the breakpoint: >=20 > (gdb) r > Starting prThread 0x7fffeffff7 In: __pthread_cond_waitu host -enable-kvm = -smp 4 -nographic -m 2G -object memory-backend-file,id=3Dmem0,size=3D2G,mem= -path=3D/dev/hugepages,share=3Don,prealloc=3Dyes, -numa node,memdev=3Dmem0 = -L88 PC: 0x7ffff772700cuThread 8 "qemu-system-x86" received signal SIGUSR= 1, User defined signal 1. > f58c1 GI_raise = = 50 = 58f7bb > #0 0x00007ffff758f7bb in __GI_raise (sig=3Dsig@entry=3D6) at ../sysdeps/= unix/sysv/linux/raise.c:50 > #1 0x00007ffff757a535 in __GI_abort () at abort.c:79 > #2 0x0000555555c9301e in kvm_set_phys_mem (kml=3D0x5555568ee830, section= =3D0x7ffff58c05e0, add=3Dtrue) at ../accel/kvm/kvm-all.c:1194 > #3 0x0000555555c930cd in kvm_region_add (listener=3D0x5555568ee830, sect= ion=3D0x7ffff58c05e0) at ../accel/kvm/kvm-all.c:1211 > #4 0x0000555555bd6c9e in address_space_update_topology_pass (as=3D0x5555= 56648420 , old_view=3D0x555556f21730, new_view=3D0x7f= fff0001cb0, adding=3Dtrue) at ../softmmu/memory.c:971 > #5 0x0000555555bd6f98 in address_space_set_flatview (as=3D0x555556648420= ) at ../softmmu/memory.c:1047 > #6 0x0000555555bd713f in memory_region_transaction_commit () at ../softm= mu/memory.c:1099 > #7 0x0000555555bd89a5 in memory_region_finalize (obj=3D0x555556e21800) a= t ../softmmu/memory.c:1751 > #8 0x0000555555cca132 in object_deinit (obj=3D0x555556e21800, type=3D0x5= 555566a8f80) at ../qom/object.c:673 > #9 0x0000555555cca1a4 in object_finalize (data=3D0x555556e21800) at ../q= om/object.c:687 > #10 0x0000555555ccb196 in object_unref (objptr=3D0x555556e21800) at ../qo= m/object.c:1186 > #11 0x0000555555bb11f0 in phys_section_destroy (mr=3D0x555556e21800) at .= ./softmmu/physmem.c:1171 > #12 0x0000555555bb124a in phys_sections_free (map=3D0x5555572cf9a0) at ..= /softmmu/physmem.c:1180 > #13 0x0000555555bb4632 in address_space_dispatch_free (d=3D0x5555572cf990= ) at ../softmmu/physmem.c:2562 > #14 0x0000555555bd4485 in flatview_destroy (view=3D0x5555572cf950) at ../= softmmu/memory.c:291 > #15 0x0000555555e367e8 in call_rcu_thread (opaque=3D0x0) at ../util/rcu.c= :281 > #16 0x0000555555e68e57 in qemu_thread_start (args=3D0x555556665e30) at ..= /util/qemu-thread-posix.c:521 > #17 0x00007ffff7720fa3 in start_thread (arg=3D) at pthread= _create.c:486lot=3D10, start=3D0xfebd1000, size=3D0x1000: File exists > #18 0x00007ffff76514cf in clone () at ../sysdeps/unix/sysv/linux/x86_64/c= lone.S:95 Yes indeed it looks alike. --=20 Peter Xu