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About Arm guests accessing to GICD_ICPENR


  • To: "julien@xxxxxxx" <julien@xxxxxxx>, Wei Chen <Wei.Chen@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Hongda Deng <Hongda.Deng@xxxxxxx>
  • Date: Mon, 6 Sep 2021 09:04:59 +0000
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  • Cc: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, nd <nd@xxxxxxx>
  • Delivery-date: Mon, 06 Sep 2021 09:05:25 +0000
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  • Thread-topic: About Arm guests accessing to GICD_ICPENR

Hi Julien,
 
Xen provides vGIC to support Xen guests, and currently xen will return IO 
unhandled when guests access GICD ICPENRn registers. This works fine with Linux 
guests, for Linux won't access these registers. But for Zephyr, this mechanism 
will cause IO dataabort on Zephyr's initialization which makes Zephyr get in 
fatal error.
 
One method to ease this is to let vGIC ignore GICD ICPENRn registers access. I 
tested it with Linux guests and Zephyr guests, and both works fine. And I found 
in this patch[1] that it would be more complex to touch the read part for 
I{S,C}PENDR and the write part for ICPENDR, so could we ignore GICD ICPENDRn 
registers access to ease Zephyr's initialization problem?

If Xen wants a complete GICD ICPENDRn emulation to fix it, do you have any 
suggestions?

[1] https://www.mail-archive.com/search?l=xen-devel@xxxxxxxxxxxxxxxxxxxx&q=
subject:%22Re%5C%3A+%5C%5BPATCH+for%5C-4.15%5C%5D+xen%5C%2Fvgic%5C%3A
+Implement+write+to+ISPENDR+in+vGICv%5C%7B2%2C+3%5C%7D%22&o=newest&f=1

Cheers
Hongda



 


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