Le 14/11/2019 à 04:46, Wangshaobo (bobo) a écrit :
Hi Christophe,
It testifys problem fixed when we use memcpy_toio() instead of memcpy In our practice, we found everything is ok before the cache_memcpy becomes memcpy in the
Patch 0b05e2d671c40cfb57e66e4e402320d6e056b2f8 adopted, it accelerates the memcpy but introduces implicit trouble, our products commonly used memcpy for continuous
matainance for a long time , but now those become a big problem for us to check where we use is correct and where is wrong, with respect to cachable_memcpy and memcpy_toio.
So, I also want to ask,
how can we trustly and unified fill the gap resulted by those changes in memcpy in version mantainance, if you have some tips pls tell me.
Tthanks, your Shaobo Wang
All accesses to I/O memory should use io accessors. Direct access to io
memory is unsafe by definition.
Incorrect accesses to I/O memory can be detected with 'sparse' tool. For
that, you just have to build the kernel with 'make vmlinux C=2' and
you'll get notified for unsafe accesses to IO memory.
Christophe
-----邮件原件-----
发件人: Christophe Leroy [mailto:christophe.leroy@xxxxxx]
发送时间: 2019年10月31日 19:13
收件人: Wangshaobo (bobo) <bobo.shaobowang@xxxxxxxxxx>
抄送: chengjian (D) <cj.chengjian@xxxxxxxxxx>; Libin (Huawei) <huawei.libin@xxxxxxxxxx>; Xiexiuqi <xiexiuqi@xxxxxxxxxx>; zhangyi (F) <yi.zhang@xxxxxxxxxx>
主题: Re: 答复: loop nesting in alignment exception and machine check
Hi,
Did you try ? Does it work ?
Christophe
Le 28/10/2019 à 06:57, Wangshaobo (bobo) a écrit :
Hi,Christophe
Thank you for your quick reply. I will try to use memcpy_toio() instead of memcpy().
-----邮件原件-----
发件人: Christophe Leroy [mailto:christophe.leroy@xxxxxx]
发送时间: 2019年10月26日 19:20
收件人: Wangshaobo (bobo) <bobo.shaobowang@xxxxxxxxxx>
抄送: linux-arch@xxxxxxxxxxxxxxx; alistair@xxxxxxxxxxxx; chengjian (D)
<cj.chengjian@xxxxxxxxxx>; Xiexiuqi <xiexiuqi@xxxxxxxxxx>;
linux-kernel@xxxxxxxxxxxxxxx; oss@xxxxxxxxxxxx; paulus@xxxxxxxxx;
Libin (Huawei) <huawei.libin@xxxxxxxxxx>; agust@xxxxxxx;
linuxppc-dev@xxxxxxxxxxxxxxxx
主题: Re: loop nesting in alignment exception and machine check
Hi,
Le 26/10/2019 à 09:23, Wangshaobo (bobo) a écrit :
Hi,
I encountered a problem about a loop nesting occurred in
manufacturing the alignment exception in machine check, trigger background is :
problem:
machine checkout or critical interrupt ->…->kbox_write[for recording
last words] -> memcpy(irremap_addr, src,size):_GLOBAL(memcpy)…
when we enter memcpy,a command ‘dcbz r11,r6’ will cause a alignment
exception, in this situation,r11 loads the ioremap address,which
leads to the alignment exception,
You can't use memcpy() on something else than memory.
For an ioremapped area, you have to use memcpy_toio()
Christophe
then the command can not be process successfully,as we still in
machine check.at the end ,it triggers a new irq machine check in irq
handler function,a loop nesting begins.
analysis:
We have analysed a lot,but it still can not come to a reasonable
description,in common,the alignment triggered in machine check
context can still be collected into the Kbox
after alignment exception be handled by handler function, but how
does the machine checkout can be triggered in the handler fucntion
for any causes? We print relevant registers
as follow when first enter machine check and alignment exception
handler
function:
MSR:0x2 MSR:0x0
SRR1:0x2 SRR1:0x21002
But the manual says SRR1 should be set to MSR(0x2),why
that happened ?
Then a branch in handler function copy the SRR1 to
MSR,this enble MSR[ME] and MSR[CE],system collapses.
Conclusion:
1) why the alignment exception can not be handled in
machine check ?
2) besides memcpy,any other function can cause the
alignment exception ?
We still recurrent it, the line as follows:
Cpu dead lock->watch log->trigger
fiq->kbox_write->memcpy->alignment exception->print last words.
but for those problems as below,what the kbox printed is empty.
------------------kbox restart:[ 10.147594]----------------
kbox verify fs magic fail
kbox mem mabye destroyed, format it
kbox: load OK
lock-task: major[249] minor[0]
-----start show_destroyed_kbox_mem_head----
00000000: 00000000 00000000 00000000 00000000 ................
00000010: 00000000 00000000 00000000 00000000 ................
00000020: 00000000 00000000 00000000 00000000 ................
00000030: 00000000 00000000 00000000 00000000 ................
00000040: 00000000 00000000 00000000 00000000 ................
00000050: 00000000 00000000 00000000 00000000 ................
00000060: 00000000 00000000 00000000 00000000 ................
00000070: 00000000 00000000 00000000 00000000 ................
00000080: 00000000 00000000 00000000 00000000 ................
00000090: 00000000 00000000 00000000 00000000 ................
