linux-kernel - Re: [RFC][PATCH 07/11] arm/tlb: Convert to generic mmu

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Message-ID: <20180919122439.GC22723@arm.com>
Date:   Wed, 19 Sep 2018 13:24:39 +0100
From:   Will Deacon <will.deacon@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     aneesh.kumar@...ux.vnet.ibm.com, akpm@...ux-foundation.org,
        npiggin@...il.com, linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux@...linux.org.uk,
        heiko.carstens@...ibm.com
Subject: Re: [RFC][PATCH 07/11] arm/tlb: Convert to generic mmu_gather

On Wed, Sep 19, 2018 at 01:28:29PM +0200, Peter Zijlstra wrote:
> On Tue, Sep 18, 2018 at 03:10:34PM +0100, Will Deacon wrote:
> 
> > So whilst I was reviewing this, I realised that I think we should be
> > selecting HAVE_RCU_TABLE_INVALIDATE for arch/arm/ if HAVE_RCU_TABLE_FREE.
> 
> Yes very much so. Let me invert that option, you normally want that,
> except if you don't natively use the linux page-tables.

Yeah, inverting this to be opt-out is definitely the safe thing to do.
Patch below looks good:

Acked-by: Will Deacon <will.deacon@....com>

Will

> ---
> Subject: asm-generic/tlb: Invert HAVE_RCU_TABLE_INVALIDATE
> From: Peter Zijlstra <peterz@...radead.org>
> Date: Wed Sep 19 13:24:41 CEST 2018
> 
> Make issuing a TLB invalidate for page-table pages the normal case.
> 
> The reason is twofold:
> 
>  - too many invalidates is safer than too few,
>  - most architectures use the linux page-tables natively
>    and would this require this.
> 
> Make it an opt-out, instead of an opt-in.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>