Re: [PATCH v2] kvm: arm64: vgic: fix hyp panic with 64k pages on juno platform

[Christoffer Dall <christoffer.dall@linaro.org>]

On Wed, Jul 30, 2014 at 11:47:40AM +0100, Marc Zyngier wrote:
> On Fri, Jul 25 2014 at  4:29:12 pm BST, Will Deacon <will.deacon@arm.com> wrote:
> > If the physical address of GICV isn't page-aligned, then we end up
> > creating a stage-2 mapping of the page containing it, which causes us to
> > map neighbouring memory locations directly into the guest.
> >
> > As an example, consider a platform with GICV at physical 0x2c02f000
> > running a 64k-page host kernel. If qemu maps this into the guest at
> > 0x80010000, then guest physical addresses 0x80010000 - 0x8001efff will
> > map host physical region 0x2c020000 - 0x2c02efff. Accesses to these
> > physical regions may cause UNPREDICTABLE behaviour, for example, on the
> > Juno platform this will cause an SError exception to EL3, which brings
> > down the entire physical CPU resulting in RCU stalls / HYP panics / host
> > crashing / wasted weeks of debugging.
> >
> > SBSA recommends that systems alias the 4k GICV across the bounding 64k
> > region, in which case GICV physical could be described as 0x2c020000 in
> > the above scenario.
> >
> > This patch fixes the problem by failing the vgic probe if the physical
> > base address or the size of GICV aren't page-aligned. Note that this
> > generated a warning in dmesg about freeing enabled IRQs, so I had to
> > move the IRQ enabling later in the probe.
> >
> > Cc: Christoffer Dall <christoffer.dall@linaro.org>
> > Cc: Marc Zyngier <marc.zyngier@arm.com>
> > Cc: Gleb Natapov <gleb@kernel.org>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: Joel Schopp <joel.schopp@amd.com>
> > Cc: Don Dutile <ddutile@redhat.com>
> > Acked-by: Peter Maydell <peter.maydell@linaro.org>
> > Signed-off-by: Will Deacon <will.deacon@arm.com>
> 
> Looks good to me:
> 
> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> 
> Christoffer, can you please take this as an urgent fix?
> 
Yes, sorry for the delay,

Applied to master and notified the KVM guys to try and get it into 3.16.

Thanks,
-Christoffer