Hi Charlie, If memory serves me right, you shouldn't need to do anything in the VirtIO devices themselves when running on KVM unless there is a bug somewhere (which I think there is, see the last paragraph).
The following discussion assumes that all devices live in a single event queue and that KVM CPUs, and only KVM CPUs, have their own event queues. I have typically used something like event queue 0 for devices and the KVM VM (KVM CPUs assume that devices use the same event queue as the KVM VM). This may be slightly different if you want to simulate multiple systems without shared memory. When encountering an MMIO operation, the CPU will automatically switch to the device's event queue by using the event queue from the KVM VM they are associated with. Interrupts are a bit more complicated, but they should normally originate from the device event queue. There are basically two ways an interrupt can happen, either it is raised as a direct consequence of an MMIO or it happens asynchronously in the device. In both cases, you will be executing in the device's event queue. The CPU ensures that's the case when performing an MMIO and asynchronous events happen as a response to an event in the device's event queue. Because of the behaviour described above, device normally never need to explicitly migrate between event queues. A quick look at the code suggests that one "unique" thing about the 9P device is that it uses the poll queue. I wouldn't be surprised if asynchronous IO handling (SIGIO and other signals) has bugs when using multiple threads in gem5. By default, the code in src/base/pollevent.cc wakes up the first event queue to service the event. However, if you look at src/sim/simulate.cc, it seems like any event queue may service events in the poll queue. This is potentially a big issue for devices that use the poll queue. A quick workaround for that issue is to add a scoped migration to the device's event queue in VirtIO9PDiod::DiodDataEvent::process(int). Cheers, Andreas On 16/03/2021 06:04, Gabe Black wrote: Basically you want to make sure you've moved to the right event queue by the time any code you call tries to schedule an event. The VirtIO devices themselves don't seem to, but the code they're calling (interacting with other devices, sending transactions to the memory system) could be. If it doesn't work in kick(), then there may be a call earlier which is causing problems. This is only necessary on code paths that are called asynchronously, like when you get poked from the other process running the diod daemon for instance. Basically you want to always and only create a ScopedMigration when called asynchronously and when something that happens during that asynchronous call might directly or indirectly cause an event to be scheduled on the event queue. I think Andreas has a lot of familiarity with this area, so hopefully he can chime in and let us know if we're on the right track. Gabe On Mon, Mar 15, 2021 at 10:39 PM Liyichao <liyic...@huawei.com<mailto:liyic...@huawei.com>> wrote: Or you mean the ScopedMigration needs to be declared in VitIO9PBase::sendMsg in fs9p.cc before kick() be called? void VirtIO9PBase::sendRMsg(const P9MsgHeader &header, const uint8_t *data, size_t size) { DPRINTF(VIO9P, "Sending RMsg\n"); EventQueue::ScopedMigration migrate(eventQueue()); dumpMsg(header, data, size); DPRINTF(VIO9P, "\tPending transactions: %i\n", pendingTransactions.size()); assert(header.len >= sizeof(header)); VirtDescriptor *main_desc(pendingTransactions[header.tag]); pendingTransactions.erase(header.tag); // Find the first output descriptor VirtDescriptor *out_desc(main_desc); while (out_desc && !out_desc->isOutgoing()) out_desc = out_desc->next(); if (!out_desc) panic("sendRMsg: Framing error, no output descriptor.\n"); P9MsgHeader header_out(htop9(header)); header_out.len = htop9(sizeof(P9MsgHeader) + size); out_desc->chainWrite(0, (uint8_t *)&header_out, sizeof(header_out)); out_desc->chainWrite(sizeof(header_out), data, size); queue.produceDescriptor(main_desc, sizeof(P9MsgHeader) + size); kick(); } ________________________________ 李翼超（Charlie） 华为技术有限公司 Huawei Technologies Co., Ltd. [Company_logo] 部门：计算系统与组件开发部 [云与计算BG] 手 机：15858232899 电子邮件：liyic...@huawei.com<mailto:liyic...@huawei.com> 地址：中国(China)-杭州(Hangzhou)-滨江区江淑路360号华为杭州研发中心Z4# [3-A06] ________________________________ 本邮件及其附件含有华为公司的保密信息，仅限于发送给上面地址中列出的个人或群组。禁 止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、或散发）本邮件中 的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！ This e-mail and its attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it! 发件人: Liyichao 发送时间: 2021年3月16日 13:30 收件人: 'Gabe Black' <gabe.bl...@gmail.com<mailto:gabe.bl...@gmail.com>> 抄送: gem5 users mailing list <gem5-users@gem5.org<mailto:gem5-users@gem5.org>> 主题: 答复: [gem5-users] gem5 crash when mount by vio-9p protocol in KVM mode with more than 1 core Hi Gabe: You mean that the code to be modified just like this? void PciVirtIO::kick() { DPRINTF(VIOIface, "kick(): Sending interrupt...\n"); EventQueue::ScopedMigration migrate(eventQueue()); interruptDeliveryPending = true; intrPost(); } void MmioVirtIO::kick() { DPRINTF(VIOIface, "kick(): Sending interrupt...\n"); EventQueue::ScopedMigration migrate(eventQueue()); setInterrupts(interruptStatus | INT_USED_RING); } 发件人: Gabe Black [mailto:gabe.bl...@gmail.com] 发送时间: 2021年3月16日 8:44 收件人: Liyichao <liyic...@huawei.com<mailto:liyic...@huawei.com>> 抄送: gem5 users mailing list <gem5-users@gem5.org<mailto:gem5-users@gem5.org>> 主题: Re: [gem5-users] gem5 crash when mount by vio-9p protocol in KVM mode with more than 1 core I think what you want to do is in the kick() functions in MmioVirtIO and PciVirtIO, you want to declare a ScopedMigration at the start of the function, and pass its constructor the result of the eventQueue() method. The SimObject class inherits from EventManager and knows what event queue it's supposed to use, and that's what eventQueue returns. When you declare a ScopedMigration, it will handle the locking correctly and move over to that queue, and when it goes out of scope (at the end of the function) it will put everything back. Please give that a try, and if it works for you (I don't have a way to test it myself) put up a review so we can get a fix checked in. Gabe On Mon, Mar 15, 2021 at 5:28 PM Liyichao <liyic...@huawei.com<mailto:liyic...@huawei.com>> wrote: Thanks for your explaination.In<https://explaination.In> O3 type with multi-core 9P is ok. 发件人： Gabe Black<gabe.bl...@gmail.com<mailto:gabe.bl...@gmail.com>> 收件人： gem5 users mailing list<gem5-users@gem5.org<mailto:gem5-users@gem5.org>> 抄送： Liyichao<liyic...@huawei.com<mailto:liyic...@huawei.com>> 主题： Re: [gem5-users] gem5 crash when mount by vio-9p protocol in KVM mode with more than 1 core 时间： 2021-03-16 07:24:15 I haven't looked at the code yet, but this is probably because the v9 implementation is getting asynchronous input which might be received by one thread, which then tries to schedule an event on an event queue associated with another queue. Most of the time this is not an issue since gem5 is usually single threaded, but when using multiple cores with KVM, each core runs in its own thread. There's a way to add events to the event queue in another thread safely (ScopedMigration) which I'm assuming the v9 code is not using. Gabe On Sun, Mar 7, 2021 at 8:38 PM Liyichao via gem5-users <gem5-users@gem5.org<mailto:gem5-users@gem5.org>> wrote: Hi All: When I use –vio-9p with fs_bigLITTLE.py, 1 core the mount cmd was ok, but more than 1 core, mount cmd will cause GEM5 crash 1core: Gem5 cmd: ./build/ARM/gem5.opt --debug-flags=Exec -d /home/l00515693/m5out configs/example/arm/fs_bigLITTLE.py --cpu-type=kvm --kernel=vmlinux --machine-type=VExpress_GEM5_V1 --disk=expanded-aarch64-ubuntu-trusty-headless.img --caches --big-cpu-clock=2.6GHz --little-cpu-clock=2.6GHz --big-cpus=1 --little-cpus=0 --mem-size=4GB --param 'system.realview.gic.gem5_extensions = True' --bootscript=./test.rcS --vio-9p Mount cmd in guest OS: mount -t 9p -o trans=virtio,version=9p2000.L,aname=/home/l00515693/m5out/9p/share gem5 /mnt/9p root@charlie:~# df -h Filesystem Size Used Avail Use% Mounted on /dev/root 9.9G 3.3G 6.2G 35% / devtmpfs 2.0G 4.0K 2.0G 1% /dev none 4.0K 0 4.0K 0% /sys/fs/cgroup none 396M 52K 396M 1% /run none 5.0M 0 5.0M 0% /run/lock none 2.0G 0 2.0G 0% /run/shm none 100M 0 100M 0% /run/user gem5 2.9T 1.8T 989G 65% /mnt/9p 2core: Gem5 cmd: ./build/ARM/gem5.opt --debug-flags=Exec -d /home/l00515693/m5out configs/example/arm/fs_bigLITTLE.py --cpu-type=kvm --kernel=vmlinux --machine-type=VExpress_GEM5_V1 --disk=expanded-aarch64-ubuntu-trusty-headless.img --caches --big-cpu-clock=2.6GHz --little-cpu-clock=2.6GHz --big-cpus=2 --little-cpus=0 --mem-size=4GB --param 'system.realview.gic.gem5_extensions = True' --bootscript=./test.rcS --vio-9p Mount cmd in guest OS: mount -t 9p -o trans=virtio,version=9p2000.L,aname=/home/l00515693/m5out/9p/share gem5 /mnt/9p GEM5 crash info: gem5.opt: build/ARM/sim/eventq_impl.hh:40: void EventQueue::schedule(Event*, Tick, bool): Assertion `when >= getCurTick()' failed. Program aborted at tick 476281849910020 --- BEGIN LIBC BACKTRACE --- ./build/ARM/gem5.opt(_Z15print_backtracev+0x40)[0xaaaadd24e418] ./build/ARM/gem5.opt(_Z12abortHandleri+0x5c)[0xaaaadd25efa4] linux-vdso.so.1(__kernel_rt_sigreturn+0x0)[0xffff9fea5688] /lib/aarch64-linux-gnu/libc.so.6(raise+0xb0)[0xffff9f6634f8] --- END LIBC BACKTRACE --- Aborted (core dumped) _______________________________________________ gem5-users mailing list -- gem5-users@gem5.org<mailto:gem5-users@gem5.org> To unsubscribe send an email to gem5-users-le...@gem5.org<mailto:gem5-users-le...@gem5.org> %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.
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