Re: [PATCH] ArmVirtPkg/ArmVirtMemoryInitPeiLib: avoid redundant cache invalidation

["Ard Biesheuvel" <ardb@kernel.org>]

On Mon, 31 Jan 2022 at 14:21, Alexander Graf <graf@amazon.com> wrote:
>
>
> On 29.01.22 16:13, Ard Biesheuvel wrote:
> > Alex reports that the cache invalidation performed by
> > ArmVirtMemoryInitPeiLib takes a non-negligible amount of time at boot.
> > This cache invalidation used to be necessary to avoid inconsistencies
> > between the CPU's cached and uncached views of the permanent PEI memory
> > region, given that the PEI phase is where the MMU gets enabled.
> >
> > The only allocations done from permanent PEI memory with the MMU off are
> > pages used for page tables, and since commit 748fea6279ef
> > ("ArmPkg/ArmMmuLib AARCH64: invalidate page tables before populating
> > them"), each of those is invalidated in the caches explicitly, for
> > reasons described in the patch's commit log. All other allocations done
> > in PEI are either from temporary PEI memory, which includes the stack,
> > or from permanent PEI memory but after the MMU has been enabled.
> >
> > This means that the cache invalidation in ArmVirtMemoryInitPeiLib is no
> > longer necessary, and can simply be dropped.
> >
> > Cc: Alexander Graf <agraf@csgraf.de>
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>
>
> Reviewed-by: Alexander Graf <graf@amazon.com>
>
> Also, feel free to add
>
> Reported-by: Alexander Graf <graf@amazon.com>
>

Merged as #2547

Thanks,