Re: [Xen-devel] [PATCH v3] xen/arm: introduce PLATFORM_QUIRK_GUEST_PIRQ_NEED_EOI

[Anup Patel <apatel@xxxxxxx>]

On Wed, Jul 9, 2014 at 7:49 PM, Stefano Stabellini
<stefano.stabellini@xxxxxxxxxxxxx> wrote:
> On Wed, 9 Jul 2014, Pranavkumar Sawargaonkar wrote:
>> Hi Stefano/ Ian,
>>
>> On Wed, Jul 9, 2014 at 6:11 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
>> > On Fri, 2014-07-04 at 15:39 +0100, Stefano Stabellini wrote:
>> >> GICH_LR_HW doesn't work as expected on X-Gene: request maintenance
>> >> interrupts and perform EOIs in the hypervisor for hardware interrupts as
>> >> a workaround.  Trigger this behaviour with a per platform option.
>> >>
>> >> This patch assumes that GICC_DIR can be written on any pcpu for a given
>> >> SGI, not matter where GICC_IAR has been read before.
>> >
>> > Did you really mean SGI here? Those are per-cpu, I suspect you meant
>> > SPI?
>> >
>> > Ack to the actual patch though.
>> >
>> > Ian.
>> >
>>
>> We have found clean fix for this issue in u-boot.
>>
>> The issue is that X-Gene does not implement security extensions
>> but the GIC-400 present in X-Gene has security extensions. To take
>> care of this situation, APM HW designers have provided two sets
>> of GIC register addresses: one for accessing GIC secured registers,
>> and another for accessing GIC non-secured registers. Currently, we
>> are only accessing GIC secured register for Linux, Xen, and KVM.
>> This works fine in most cases but does not work for GICH_LRn.HW
>> bit because we can only auto-deactivate non-secured interrupts using
>> GICH_LRn.HW bit.
>>
>> To fix this issue, we have updated u-boot to initialize GIC secured
>> register to make all interrupts as non-secured and we will need to
>> access GIC non-secured registers from Linux, Xen, KVM, and
>> everywhere else.
>>
>> For now, you can go ahead with this patch but once we have updated
>> u-boot released by APM then we will need to disable the quirk for
>> X-Gene Mustang. We would be also having a patch for Linux to fix
>> the GIC addresses in X-Gene Storm DTS file.
>
> It's great that you managed to fix the problem!
>
> How can we detect whether the Mustang board we are running on has an
> up-to-date uboot? Would it be possible for u-boot to add a flag
> somewhere to tell that the GICH_LRn.HW is safe to use? Then we could
> check that flag and only enable PLATFORM_QUIRK_GUEST_PIRQ_NEED_EOI if
> the flag is missing.

I think we should check GIC Dist address passed in DTS by
u-boot to Xen. If GIC Dist address is secured address then
enable the quirk otherwise disable the qurik.

Regards,
Anup

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