Re: [Qemu-devel] [PATCH v4 21/21] hw/arm/virt: Add support for Cortex-A57

[Peter Maydell <peter.maydell@linaro.org>]

On 10 April 2014 20:41, Rob Herring <robherring2@gmail.com> wrote:
> On Thu, Apr 10, 2014 at 10:02 AM, Peter Maydell
> <peter.maydell@linaro.org> wrote:
>> We could in theory write an a57mpcore_priv which was a
>> carbon copy of a15mpcore_priv, but that seems a bit pointless.
>> I think it's probably actually reasonable to use a15mpcore_priv
>> here, with an appropriate comment:
>>
>>     /* Our A57 has an A15-style GICv2, so we can use a15mpcore_priv */
>
> I think there are 3 possibilities of what actual h/w may look like. i
> agree this is the correct thing to do for one case (and is the only
> one qemu is able to support today). The others are:
>
> A57 + SBSA compliant GICv2(M)
> A57 + GICv3
>
> The SBSA change is making each register bank within the GIC 64K spaced
> instead of 4K spaced to support 64KB pages in OSs and hypervisors.

That part is pretty easy to do in QEMU -- we'd just need a suitable
container object that mapped the GIC regions in different locations.
It might be worth doing that now rather than putting this in and
then changing it later.

> This is a simple address swizzling trick defined in the SBSA doc.
> (Since it's documented it must not be a cute embedded nonsense hack.
> :)) Then the M portion is for PCI MSI support which is optional.

I haven't looked too closely at the GICv2M spec but it probably
is not too hard (certainly in comparison to the v3 GIC ;-))

thanks
-- PMM