Re: [Xen-devel] [PATCH v3 16/16] xen/arm: arm64: Document Cortex-A57 erratum 834220

[Julien Grall <julien.grall@xxxxxxx>]

Hello,

On 07/06/16 17:06, Julien Grall wrote:
> The ARM erratum applies to certain revisions of Cortex-A57. The
> processor may report a Stage 2 translation fault as the result of
> Stage 1 fault for load crossing a page boundary when there is a
> permission fault or device memory fault at stage 1 and a translation
> fault at Stage 2.
>
> So Xen needs to check that Stage 1 translation does not generate a fault
> before handling the Stage 2 fault. If it is a Stage 1 translation fault,
> return to the guest to let the processor injecting the correct fault.
>
> Only document it as this is already the behavior of the fault handlers.
> Note that some optimization could be done to avoid unnecessary translation
> fault. This is because HPFAR_EL2 is valid for more use case. For the moment,
> the code is left unmodified.
>
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
Actually I am working on a patch series to optimize the data handles 
(i.e to avoid unnecessary translation). I don't think the documentation 
is strictly necessary for now. So I will drop this patch and implement 
the workaround on top of the other series.
Regards,

--
Julien Grall

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