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Mon, 19 Jul 2021 18:02:08 +0000 From: Thanos Makatos To: Peter Xu Subject: Re: Question on memory commit during MR finalize() Thread-Topic: Question on memory commit during MR finalize() Thread-Index: AQHWF1blDKoce5BcwE+aLVbWV0XOZKiCivmAgAAd6oCAAKsXAIAAEMEAgsN1h+CAAEdvgIABHU1QgAAtSoCABLlmgIAAGMwAgAAi0xQ= Date: Mon, 19 Jul 2021 18:02:08 +0000 Message-ID: References: <20200420210049.GA420399@xz-x1> <20200420233115.GB420399@xz-x1> <5ed295a3-9e4a-0dca-adc6-5361dc78a83c@redhat.com> <20200421104334.GC420399@xz-x1> , In-Reply-To: Accept-Language: en-GB, en-US Content-Language: en-GB X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: redhat.com; dkim=none (message not signed) header.d=none;redhat.com; dmarc=none action=none header.from=nutanix.com; x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: f2452856-1148-4e61-1377-08d94adf5371 x-ms-traffictypediagnostic: CH2PR02MB6455: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-proofpoint-crosstenant: true x-ms-oob-tlc-oobclassifiers: OLM:249; 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envelope-from=thanos.makatos@nutanix.com; helo=mx0a-002c1b01.pphosted.com X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) DKIMWL_WL_HIGH=-1.469, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, HTML_MESSAGE=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" --_000_CH0PR02MB789857DE73B0A9B1FC29593E8BE19CH0PR02MB7898namp_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Omg I don't know how I missed that, of course I'll ignore SIGUSR1 and retes= t! ________________________________ From: Peter Xu Sent: Monday, 19 July 2021, 16:58 To: Thanos Makatos Cc: Paolo Bonzini; Markus Armbruster; QEMU Devel Mailing List; John Levon; = John G Johnson Subject: Re: Question on memory commit during MR finalize() Hi, Thanos, On Mon, Jul 19, 2021 at 02:38:52PM +0000, Thanos Makatos wrote: > I can trivially trigger an assertion with a build where I merged the rece= nt vfio-user patches (https://urldefense.proofpoint.com/v2/url?u=3Dhttps-3A= __patchew.org_QEMU_cover.1626675354.git.elena.ufimtseva-40oracle.com_&d=3DD= wIBaQ&c=3Ds883GpUCOChKOHiocYtGcg&r=3DXTpYsh5Ps2zJvtw6ogtti46atk736SI4vgsJiU= KIyDE&m=3DLvALaULnrxZWlgXFcaxGAl95UIwq3a6LI8OnG_5r4XY&s=3DmoFPVchYp27xozQcv= vxG4nb4nC2QmMnqQ1Wmt4Z3dNE&e=3D ) to master and then merging the result int= o your xzpeter/memory-sanity branch, I've pushed the branch here: https://u= rldefense.proofpoint.com/v2/url?u=3Dhttps-3A__github.com_tmakatos_qemu_tree= _memory-2Dsanity&d=3DDwIBaQ&c=3Ds883GpUCOChKOHiocYtGcg&r=3DXTpYsh5Ps2zJvtw6= ogtti46atk736SI4vgsJiUKIyDE&m=3DLvALaULnrxZWlgXFcaxGAl95UIwq3a6LI8OnG_5r4XY= &s=3DveyjdkkFkGSYNDZOuksB-kbHmdQaw9RYxyZp8Qo7nW4&e=3D . I explain the repro= steps below in case you want to take a look: > > Build as follows: > > ./configure --prefix=3D/opt/qemu-xzpeter --target-list=3Dx86_64-softmmu -= -enable-kvm --enable-debug --enable-multiprocess && make -j `nproc` && mak= e install > > Then build and run the GPIO sample from libvfio-user (https://urldefense.= proofpoint.com/v2/url?u=3Dhttps-3A__github.com_nutanix_libvfio-2Duser&d=3DD= wIBaQ&c=3Ds883GpUCOChKOHiocYtGcg&r=3DXTpYsh5Ps2zJvtw6ogtti46atk736SI4vgsJiU= KIyDE&m=3DLvALaULnrxZWlgXFcaxGAl95UIwq3a6LI8OnG_5r4XY&s=3DHYP5NmDMGuS13pdyV= 83x3HzyhGbE-oP1T8NLtu0d1U8&e=3D ): > > libvfio-user/build/dbg/samples/gpio-pci-idio-16 -v /var/run/vfio-user.soc= k > > And then run QEMU as follows: > > gdb --args /opt/qemu-xzpeter/bin/qemu-system-x86_64 -cpu host -enable-kvm= -smp 4 -m 2G -object memory-backend-file,id=3Dmem0,size=3D2G,mem-path=3D/d= ev/hugepages,share=3Don,prealloc=3Dyes -numa node,memdev=3Dmem0 -kernel bio= nic-server-cloudimg-amd64-vmlinuz-generic -initrd bionic-server-cloudimg-am= d64-initrd-generic -append 'console=3DttyS0 root=3D/dev/sda1 single' -hda b= ionic-server-cloudimg-amd64-0.raw -nic user,model=3Dvirtio-net-pci -machine= pc-q35-3.1 -device vfio-user-pci,socket=3D/var/run/vfio-user.sock -nograph= ic > > I immediately get the following stack trace: > > Thread 5 "qemu-system-x86" received signal SIGUSR1, User defined signal 1= . This is SIGUSR1. QEMU uses it for general vcpu ipis. > [Switching to Thread 0x7fffe6e82700 (LWP 151973)] > __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:10= 3 > 103 ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S: No such file or= directory. > (gdb) bt > #0 0x00007ffff655d29c in __lll_lock_wait () at ../sysdeps/unix/sysv/linu= x/x86_64/lowlevellock.S:103 > #1 0x00007ffff6558642 in __pthread_mutex_cond_lock (mutex=3Dmutex@entry= =3D0x5555568bb280 ) at ../nptl/pthread_mutex_lock.c:80 > #2 0x00007ffff6559ef8 in __pthread_cond_wait_common (abstime=3D0x0, mute= x=3D0x5555568bb280 , cond=3D0x555556cecc30) at pthread_c= ond_wait.c:645 > #3 0x00007ffff6559ef8 in __pthread_cond_wait (cond=3D0x555556cecc30, mut= ex=3D0x5555568bb280 ) at pthread_cond_wait.c:655 > #4 0x000055555604f717 in qemu_cond_wait_impl (cond=3D0x555556cecc30, mut= ex=3D0x5555568bb280 , file=3D0x5555561ca869 "../softmmu/= cpus.c", line=3D514) at ../util/qemu-thread-posix.c:194 > #5 0x0000555555d28a4a in qemu_cond_wait_iothread (cond=3D0x555556cecc30)= at ../softmmu/cpus.c:514 > #6 0x0000555555d28781 in qemu_wait_io_event (cpu=3D0x555556ce02c0) at ..= /softmmu/cpus.c:425 > #7 0x0000555555e5da75 in kvm_vcpu_thread_fn (arg=3D0x555556ce02c0) at ..= /accel/kvm/kvm-accel-ops.c:54 > #8 0x000055555604feed in qemu_thread_start (args=3D0x555556cecc70) at ..= /util/qemu-thread-posix.c:541 > #9 0x00007ffff6553fa3 in start_thread (arg=3D) at pthread= _create.c:486 > #10 0x00007ffff64824cf in clone () at ../sysdeps/unix/sysv/linux/x86_64/c= lone.S:95 Would you please add below to your ~/.gdbinit script? handle SIGUSR1 nostop noprint Or just run without gdb and wait it to crash with SIGABRT. Thanks, -- Peter Xu --_000_CH0PR02MB789857DE73B0A9B1FC29593E8BE19CH0PR02MB7898namp_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable
Omg I don't know how I missed that, of course I'll ignore SIGUSR1 and retes= t!

From: Peter Xu <peterx@redhat= .com>
Sent: Monday, 19 July 2021, 16:58
To: Thanos Makatos
Cc: Paolo Bonzini; Markus Armbruster; QEMU Devel Mailing L= ist; John Levon; John G Johnson
Subject: Re: Question on memory commit during MR finalize(= )

Hi, Thanos,

On Mon, Jul 19, 2021 at 02:38:52PM +0000, Thanos Makatos wrote:
> I can trivially trigger an assertion with a build where I merged the r= ecent vfio-user patches (https://urldefense.proofpoint.com= /v2/url?u=3Dhttps-3A__patchew.org_QEMU_cover.1626675354.git.elena.ufimtseva= -40oracle.com_&d=3DDwIBaQ&c=3Ds883GpUCOChKOHiocYtGcg&r=3DXTpYsh= 5Ps2zJvtw6ogtti46atk736SI4vgsJiUKIyDE&m=3DLvALaULnrxZWlgXFcaxGAl95UIwq3= a6LI8OnG_5r4XY&s=3DmoFPVchYp27xozQcvvxG4nb4nC2QmMnqQ1Wmt4Z3dNE&e=3D ) to master and then merging the result into your xzpeter/memory-sanity br= anch, I've pushed the branch here: https://urldefense.proofpoint.com/v2/url?u=3Dhttps-3A__github.com_tmakatos_= qemu_tree_memory-2Dsanity&d=3DDwIBaQ&c=3Ds883GpUCOChKOHiocYtGcg&= ;r=3DXTpYsh5Ps2zJvtw6ogtti46atk736SI4vgsJiUKIyDE&m=3DLvALaULnrxZWlgXFca= xGAl95UIwq3a6LI8OnG_5r4XY&s=3DveyjdkkFkGSYNDZOuksB-kbHmdQaw9RYxyZp8Qo7n= W4&e=3D . I explain the repro steps below in case you want to take a look:
>
> Build as follows:
>
> ./configure --prefix=3D/opt/qemu-xzpeter --target-list=3Dx86_64-softmm= u --enable-kvm  --enable-debug --enable-multiprocess && make -= j `nproc` && make install
>
> Then build and run the GPIO sample from libvfio-user (https://urldefense.proofpoint.com/v2/url?u=3Dhttps-3A__github.com_nutanix_= libvfio-2Duser&d=3DDwIBaQ&c=3Ds883GpUCOChKOHiocYtGcg&r=3DXTpYsh= 5Ps2zJvtw6ogtti46atk736SI4vgsJiUKIyDE&m=3DLvALaULnrxZWlgXFcaxGAl95UIwq3= a6LI8OnG_5r4XY&s=3DHYP5NmDMGuS13pdyV83x3HzyhGbE-oP1T8NLtu0d1U8&e=3D ):
>
> libvfio-user/build/dbg/samples/gpio-pci-idio-16 -v /var/run/vfio-user.= sock
>
> And then run QEMU as follows:
>
> gdb --args /opt/qemu-xzpeter/bin/qemu-system-x86_64 -cpu host -enable-= kvm -smp 4 -m 2G -object memory-backend-file,id=3Dmem0,size=3D2G,mem-path= =3D/dev/hugepages,share=3Don,prealloc=3Dyes -numa node,memdev=3Dmem0 -kerne= l bionic-server-cloudimg-amd64-vmlinuz-generic -initrd bionic-server-cloudimg-amd64-initrd-generic -append 'console=3DttyS0 root= =3D/dev/sda1 single' -hda bionic-server-cloudimg-amd64-0.raw -nic user,mode= l=3Dvirtio-net-pci -machine pc-q35-3.1 -device vfio-user-pci,socket=3D/var/= run/vfio-user.sock -nographic
>
> I immediately get the following stack trace:
>
> Thread 5 "qemu-system-x86" received signal SIGUSR1, User def= ined signal 1.

This is SIGUSR1.  QEMU uses it for general vcpu ipis.

> [Switching to Thread 0x7fffe6e82700 (LWP 151973)]
> __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S= :103
> 103     ../sysdeps/unix/sysv/linux/x86_64/lowlevel= lock.S: No such file or directory.
> (gdb) bt
> #0  0x00007ffff655d29c in __lll_lock_wait () at ../sysdeps/unix/s= ysv/linux/x86_64/lowlevellock.S:103
> #1  0x00007ffff6558642 in __pthread_mutex_cond_lock (mutex=3Dmute= x@entry=3D0x5555568bb280 <qemu_global_mutex>) at ../nptl/pthread_mute= x_lock.c:80
> #2  0x00007ffff6559ef8 in __pthread_cond_wait_common (abstime=3D0= x0, mutex=3D0x5555568bb280 <qemu_global_mutex>, cond=3D0x555556cecc30= ) at pthread_cond_wait.c:645
> #3  0x00007ffff6559ef8 in __pthread_cond_wait (cond=3D0x555556cec= c30, mutex=3D0x5555568bb280 <qemu_global_mutex>) at pthread_cond_wait= .c:655
> #4  0x000055555604f717 in qemu_cond_wait_impl (cond=3D0x555556cec= c30, mutex=3D0x5555568bb280 <qemu_global_mutex>, file=3D0x5555561ca86= 9 "../softmmu/cpus.c", line=3D514) at ../util/qemu-thread-posix.c= :194
> #5  0x0000555555d28a4a in qemu_cond_wait_iothread (cond=3D0x55555= 6cecc30) at ../softmmu/cpus.c:514
> #6  0x0000555555d28781 in qemu_wait_io_event (cpu=3D0x555556ce02c= 0) at ../softmmu/cpus.c:425
> #7  0x0000555555e5da75 in kvm_vcpu_thread_fn (arg=3D0x555556ce02c= 0) at ../accel/kvm/kvm-accel-ops.c:54
> #8  0x000055555604feed in qemu_thread_start (args=3D0x555556cecc7= 0) at ../util/qemu-thread-posix.c:541
> #9  0x00007ffff6553fa3 in start_thread (arg=3D<optimized out&g= t;) at pthread_create.c:486
> #10 0x00007ffff64824cf in clone () at ../sysdeps/unix/sysv/linux/x86_6= 4/clone.S:95

Would you please add below to your ~/.gdbinit script?

  handle SIGUSR1 nostop noprint

Or just run without gdb and wait it to crash with SIGABRT.

Thanks,

--
Peter Xu


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