linux-kernel - Re: [PATCH v2 2/4] ioremap: Implement TLB

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Message-ID: <20180315151645.fsgcywyawvtiwx52@lakrids.cambridge.arm.com>
Date:   Thu, 15 Mar 2018 15:16:45 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Chintan Pandya <cpandya@...eaurora.org>
Cc:     catalin.marinas@....com, will.deacon@....com, arnd@...db.de,
        ard.biesheuvel@...aro.org, marc.zyngier@....com,
        james.morse@....com, kristina.martsenko@....com,
        takahiro.akashi@...aro.org, gregkh@...uxfoundation.org,
        tglx@...utronix.de, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        akpm@...ux-foundation.org, toshi.kani@....com
Subject: Re: [PATCH v2 2/4] ioremap: Implement TLB_INV before huge mapping

On Thu, Mar 15, 2018 at 06:55:32PM +0530, Chintan Pandya wrote:
> On 3/15/2018 6:43 PM, Mark Rutland wrote:
> > On Thu, Mar 15, 2018 at 06:15:04PM +0530, Chintan Pandya wrote:
> > > Huge mapping changes PMD/PUD which could have
> > > valid previous entries. This requires proper
> > > TLB maintanance on some architectures, like
> > > ARM64.
> > 
> > Just to check, I take it that you mean we could have a valid table
> > entry, but all the entries in that next level table must be invalid,
> > right?
> 
> That was my assumption but my assumption can be wrong if any VA gets
> block mapping for 1G directly (instead of the 2M cases we discussed
> so far), then this would go for a toss.

Ok. Just considering the 4K -> 2M case, is that an assumption, or a
guarantee?

Thanks,
Mark.