linux-kernel - Re: icache_is_aliasing and big.LITTLE

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Date:   Thu, 9 May 2019 11:14:07 -0700
From:   Salman Qazi <sqazi@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: icache_is_aliasing and big.LITTLE

Thank you.

On Thu, May 9, 2019 at 1:50 AM Catalin Marinas <catalin.marinas@....com> wrote:
>
> Hi,
>
> On Wed, May 08, 2019 at 11:45:03AM -0700, Salman Qazi wrote:
> > What is the intention behind icache_is_aliasing on big.LITTLE systems
> > where some icaches are VIPT and others are PIPT? Is it meant to be
> > conservative in some sense or should it be made per-CPU?
>
> It needs to cover the worst case scenario across all CPUs, i.e. aliasing
> VIPT if one of the CPUs has this. We can't make it per-CPU because a
> thread performing cache maintenance might be migrated to another CPU
> with different cache policy (e.g. sync_icache_aliases()).
>
> --
> Catalin