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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

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.

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