Messages in this thread |  | | From | Zhangfei Gao <> | Date | Sun, 24 Apr 2022 10:58:10 +0800 | Subject | Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit |
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On Sat, 23 Apr 2022 at 19:13, zhangfei.gao@foxmail.com <zhangfei.gao@foxmail.com> wrote: > > Hi, Jean > > On 2022/4/22 下午11:50, Jean-Philippe Brucker wrote: > > On Fri, Apr 22, 2022 at 09:15:01PM +0800, zhangfei.gao@foxmail.com wrote: > >>> I'm trying to piece together what happens from the kernel point of view. > >>> > >>> * master process with mm A opens a queue fd through uacce, which calls > >>> iommu_sva_bind_device(dev, A) -> PASID 1 > >>> > >>> * master forks and exits. Child (daemon) gets mm B, inherits the queue fd. > >>> The device is still bound to mm A with PASID 1, since the queue fd is > >>> still open. > >>> We discussed this before, but I don't remember where we left off. The > >>> child can't use the queue because its mappings are not copied on fork(), > >>> and the queue is still bound to the parent mm A. The child either needs to > >>> open a new queue or take ownership of the old one with a new uacce ioctl. > >> Yes, currently nginx aligned with the case. > >> Child process (worker process) reopen uacce, > >> > >> Master process (do init) open uacce, iommu_sva_bind_device(dev, A) -> PASID > >> 1 > >> Master process fork Child (daemon) and exit. > >> > >> Child (daemon) does not use PASID 1 any more, only fork and manage worker > >> process. > >> Worker process reopen uacce, iommu_sva_bind_device(dev, B) PASID 2 > >> > >> So it is expected. > > Yes, that's fine > > > >>> Is that the "IMPLEMENT_DYNAMIC_BIND_FN()" you mention, something out of > >>> tree? This operation should unbind from A before binding to B, no? > >>> Otherwise we leak PASID 1. > >> In 5.16 PASID 1 from master is hold until nginx service stop. > >> nginx start > >> master: > >> iommu_sva_alloc_pasid mm->pasid=1 // master process > >> > >> lynx https start: > >> iommu_sva_alloc_pasid mm->pasid=2 //worker process > >> > >> nginx stop: from fops_release > >> iommu_sva_free_pasid mm->pasid=2 // worker process > >> iommu_sva_free_pasid mm->pasid=1 // master process > > That's the expected behavior (master could close its fd before forking, in > > order to free things up earlier, but it's not mandatory) > Currently we unbind in fops_release, so the ioasid allocated in master > can only be freed when nginx stop, > when all forked fd are closed. > > > > >> Have one silly question. > >> > >> kerne driver > >> fops_open > >> iommu_sva_bind_device > >> > >> fops_release > >> iommu_sva_unbind_device > >> > >> application > >> main() > >> fd = open > >> return; > >> > >> Application exit but not close(fd), is it expected fops_release will be > >> called automatically by system? > > Yes, the application doesn't have to call close() explicitly, the file > > descriptor is closed automatically on exit. Note that the fd is copied on > > fork(), so it is only released once parent and all child processes exit. > Yes, in case the application ended unexpected, like ctrl+c > > > >> On 5.17 > >> fops_release is called automatically, as well as iommu_sva_unbind_device. > >> On 5.18-rc1. > >> fops_release is not called, have to manually call close(fd) > > Right that's weird > Looks it is caused by the fix patch, via mmget, which may add refcount > of fd. > > Some experiments > 1. 5.17, everything works well. > > 2. 5.17 + patchset of "iommu/sva: Assign a PASID to mm on PASID > allocation and free it on mm exit" > > Test application, exit without close uacce fd > First time: fops_release can be called automatically. > > log: > ioasid_alloc ioasid=1 > iommu_sva_alloc_pasid pasid=1 > iommu_sva_bind_device handle=00000000263a2ee8 > ioasid_free ioasid=1 > uacce_fops_release q=0000000055ca3cdf > iommu_sva_unbind_device handle=00000000263a2ee8 > > Second time: hardware reports error > > uacce_fops_open q=000000008e4d6f78 > ioasid_alloc ioasid=1 > iommu_sva_alloc_pasid pasid=1 > iommu_sva_bind_device handle=00000000cfd11788 > // Haredware reports error > hisi_sec2 0000:b6:00.0: qm_acc_do_task_timeout [error status=0x20] found > hisi_sec2 0000:b6:00.0: qm_acc_wb_not_ready_timeout [error status=0x40] > found > hisi_sec2 0000:b6:00.0: sec_fsm_hbeat_rint [error status=0x20] found > hisi_sec2 0000:b6:00.0: Controller resetting... > hisi_sec2 0000:b6:00.0: QM mailbox operation timeout! > hisi_sec2 0000:b6:00.0: Failed to dump sqc! > hisi_sec2 0000:b6:00.0: Failed to drain out data for stopping! > hisi_sec2 0000:b6:00.0: Bus lock! Please reset system. > hisi_sec2 0000:b6:00.0: Controller reset failed (-110) > hisi_sec2 0000:b6:00.0: controller reset failed (-110) > > 3. Add the fix patch of using mmget in bind. > Test application, exit without close uacce fd > > fops_release can NOT be called automatically, looks mmget adds refcount > of fd.
Test application, exit without closing fd. > >> kernel driver > >> fops_open > >> iommu_sva_bind_device > >> > >> fops_release > >> iommu_sva_unbind_device
1. 5.17 kernel, no mmget & mmput
wd_release_queue no close Compress bz=512000 nb=1×10, speed=139.5 MB/s (±0.0% N=1) overall=122.9 MB/s (±0.0%) [ 16.052989] do_exit current=d380000 [ 16.053828] mmput atomic=1 [ 16.054511] __mmput atomic=0 [ 16.070382] exit_task_work [ 16.070981] uacce_fops_release current=d380000 [ 16.071999] CPU: 0 PID: 176 Comm: test_sva_perf Not tainted 5.16.0-rc1-27342-ge5f9f3f99a88-dirty #240 [ 16.074007] Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 [ 16.075530] Call trace: [ 16.076069] dump_backtrace+0x0/0x1a0 [ 16.076887] show_stack+0x20/0x30 [ 16.077629] dump_stack_lvl+0x8c/0xb8 [ 16.078441] dump_stack+0x18/0x34 [ 16.079176] uacce_fops_release+0x44/0xdc [ 16.080060] __fput+0x78/0x240 [ 16.080743] ____fput+0x18/0x28 [ 16.081447] task_work_run+0x88/0x160 [ 16.082259] do_exit+0x52c/0xa50 [ 16.082974] do_group_exit+0x84/0xa8 [ 16.083768] __wake_up_parent+0x0/0x38 [ 16.084597] invoke_syscall+0x4c/0x110 [ 16.085435] el0_svc_common.constprop.0+0x68/0x128 [ 16.086501] do_el0_svc+0x2c/0x90 [ 16.087243] el0_svc+0x24/0x70 [ 16.087928] el0t_64_sync_handler+0xb0/0xb8 [ 16.088854] el0t_64_sync+0x1a0/0x1a4 [ 16.089775] arm_smmu_sva_unbind [ 16.090577] iommu_sva_free_pasid mm->pasid=1 [ 16.091763] exit_task_work done
2. Add mmget in bind and mmput in unbind, Since application do not close fd, so no unbind,& mmput And fops_release is not called since mm_users account.
log: [ 101.642690] mmput atomic=3 wd_release_queue no close Compress bz=512000 nb=1×10, speed=40.3 MB/s (±0.0% N=1) overall=38.7 MB/s (±0.0%) [ 101.671167] do_exit current=d9daf40 [ 101.672003] mmput atomic=2 [ 101.672712] exit_task_work [ 101.673292] exit_task_work done
Thanks
> > So the fix method of using mmget blocks fops_release to be called once > fd is closed without unbind. > > >> Since nginx may have a issue, it does not call close(fd) when nginx -s quit. > > And you're sure that none of the processes are still alive or in zombie > > state? Just to cover every possibility. > It can also reproduced by a simple application exit without close(uacce_fd) > > Thanks >
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