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[Xen-devel] Legacy PIC (x86) support (RTC) in dom0 with Linux 4.12 and newer is broken for some hardware.


  • To: "'xen-devel@xxxxxxxxxxxxxxxxxxxx'" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Jennifer Herbert <jennifer.herbert@xxxxxxxxxx>
  • Date: Tue, 4 Dec 2018 17:24:08 +0000
  • Accept-language: en-GB, en-US
  • Delivery-date: Tue, 04 Dec 2018 17:47:54 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Thread-index: AdSL9ao0uOEkIcTIT5asq4bk4/TUUg==
  • Thread-topic: Legacy PIC (x86) support (RTC) in dom0 with Linux 4.12 and newer is broken for some hardware.

Since Linux 4.12, there has been a commit a1e23a42f1bdc00e32fc4869caef12e4e6272f26
“rtc: cmos: Do not assume irq 8 for rtc when there are no legacy irqs”
 
The commit effectively disabled requesting IRQ 8 for systems without PIC
controller present (As in the case when used at dom0 under Xen) and at
the same time where this IRQ is not explicitly described in ACPI tables.
 
I have found hardware without this IRQ in the ACPI tables, and indeed,
found the RTC to be broken in dom 0.  Temporarily, I reverted this
commit, which fixed the problem, but I was wondering if anyone here
knew of a better solution?

 

Cheers,

 

-jenny

 

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