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    SubjectRe: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit
    On 4/11/22 07:00, Zhangfei Gao wrote:
    > with this patchset, each time after sbin/nginx, ioasid is freed
    > immediately. lynx test will alloc the same ioasid=1.

    That doesn't seem right. Isn't 'sbin/nginx' still running when lynx
    runs? How can they get the same ioasid?

    This sounds like a refcounting problem, like that the ioasid wasn't
    properly refcounted as nginx forked into the background.

    > To verify, hack comment mm_pasid_drop in __mmput will make the issue
    > disappear.
    >
    > log: after sbin/nginx.
    > [   96.526730] Call trace:
    > [   96.526732]  dump_backtrace+0xe4/0xf0
    > [   96.526741]  show_stack+0x20/0x70
    > [   96.526744]  dump_stack_lvl+0x8c/0xb8
    > [   96.526751]  dump_stack+0x18/0x34
    > [   96.526754]  ioasid_free+0xdc/0xfc
    > [   96.526757]  mmput+0x138/0x160
    > [   96.526760]  do_exit+0x284/0x9d0
    > [   96.526765]  do_group_exit+0x3c/0xa8
    > [   96.526767]  __wake_up_parent+0x0/0x38
    > [   96.526770]  invoke_syscall+0x4c/0x110
    > [   96.526775]  el0_svc_common.constprop.0+0x68/0x128
    > [   96.526778]  do_el0_svc+0x2c/0x90
    > [   96.526781]  el0_svc+0x30/0x98
    > [   96.526783]  el0t_64_sync_handler+0xb0/0xb8
    > [   96.526785]  el0t_64_sync+0x18c/0x190

    Is there nothing before this call trace? Usually there will be at least
    some warning text.

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