# 'invalidateLocalTLB()' blocked in sel4 kernel

**URL:** <https://sel4.discourse.group/t/invalidatelocaltlb-blocked-in-sel4-kernel/427>\
**Category:** seL4 kernel\
**Tags:** arm\
**Created:** [October 22, 2021, 12:59am UTC](https://sel4.discourse.group/t/invalidatelocaltlb-blocked-in-sel4-kernel/427 "2021-10-22T00:59:21Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![chenSevenHalf](https://yyz2.discourse-cdn.com/free1/user_avatar/sel4.discourse.group/chensevenhalf/32/136_2.png) [@chenSevenHalf](https://sel4.discourse.group/u/chenSevenHalf)\
**Post date:** [October 22, 2021, 12:59am UTC](https://sel4.discourse.group/t/invalidatelocaltlb-blocked-in-sel4-kernel/427/1 "2021-10-22T00:59:21Z")

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when I try port the sel4 to my **imx6ull** (cortex a7) development board，I’ve adapted the sel4 codes, but it does not work. When it run init\_kernel-\>try\_init\_kernel-\>init\_cpu-\>activate\_global\_pd-\>invalidateLocalTLB-\>asm volatile(“mcr p15, 0, %0, c8, c7, 0” : : “r”(0)), it just trapped. If I comment out the line asm ‘volatile(“mcr p15, 0, %0, c8, c7, 0” : : “r”(0))’, then it works and runs untill the end of the sel4test. The situation also appears when I port another board (cortex A55). Does anyone meet this? and how can I do? by the way, I start the sel4 image by uboot.

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**Author:** ![chenSevenHalf](https://yyz2.discourse-cdn.com/free1/user_avatar/sel4.discourse.group/chensevenhalf/32/136_2.png) [@chenSevenHalf](https://sel4.discourse.group/u/chenSevenHalf)\
**Post date:** [October 26, 2021, 5:44am UTC](https://sel4.discourse.group/t/invalidatelocaltlb-blocked-in-sel4-kernel/427/2 "2021-10-26T05:44:38Z")

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Oh，I solved the problem by myself. When the ‘invalidateLocalTLB’ is called, the printf should not use the physical address. and 'printf ’ should not be used before ‘init\_cpu’.

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**Author:** ![gerwin.klein](https://yyz2.discourse-cdn.com/free1/user_avatar/sel4.discourse.group/gerwin.klein/32/46_2.png) [@gerwin.klein](https://sel4.discourse.group/u/gerwin.klein)\
**Post date:** [October 26, 2021, 11:48pm UTC](https://sel4.discourse.group/t/invalidatelocaltlb-blocked-in-sel4-kernel/427/3 "2021-10-26T23:48:10Z")

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Thanks for posting the solution!