Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 9 May 2019 09:50:04 +0100
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Salman Qazi <sqazi@google.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: icache_is_aliasing and big.LITTLE
Message-ID: <20190509085004.GE64514@C02TF0J2HF1T.local>
References: <CAKUOC8WxRnzeMEcS-vao-GOzXnF+FN+3uk8R6TspRj23V7kYJQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAKUOC8WxRnzeMEcS-vao-GOzXnF+FN+3uk8R6TspRj23V7kYJQ@mail.gmail.com>
User-Agent: Mutt/1.11.2 (2019-01-07)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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