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

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

[Jennifer Herbert]

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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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Re: Legacy PIC (x86) support (RTC) in dom0 with Linux 4.12 and newer is broken for some hardware.

[Jennifer Herbert]

CC: Juergen Gross

On 04/12/18 17:24, Jennifer Herbert wrote:
> Since Linux 4.12, there has been a commita1e23a42f1bdc00e32fc4869caef12e4e6272f26
>
> “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
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xenproject.org
> https://lists.xenproject.org/mailman/listinfo/xen-devel
>

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Re: Legacy PIC (x86) support (RTC) in dom0 with Linux 4.12 and newer is broken for some hardware.

[Juergen Gross]

On 05/12/2018 17:40, Jennifer Herbert wrote:
> CC: Juergen Gross
> 
> On 04/12/18 17:24, Jennifer Herbert wrote:
>> Since Linux 4.12, there has been a
>> commita1e23a42f1bdc00e32fc4869caef12e4e6272f26
>>
>> “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?

Usage of a Xen-specific struct legacy_pic?


Juergen

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