linux-kernel - Re: [patch 00/15] x86/tlb: Unexport per-CPU tlbstate

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Message-ID: <913b9a53-1df4-e371-a3d8-867d1242c341@oracle.com>
Date:   Mon, 20 Apr 2020 18:58:54 +0200
From:   Alexandre Chartre <alexandre.chartre@...cle.com>
To:     Christoph Hellwig <hch@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Kees Cook <keescook@...omium.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Lendacky <Thomas.Lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [patch 00/15] x86/tlb: Unexport per-CPU tlbstate

On 4/20/20 11:20 AM, Christoph Hellwig wrote:
> Just looking over some exports at the end of the series (and thus
> ignoring bisection issues):
> 
>   - Is there any good reason to keep __flush_tlb_all inline vs moving it
>     out of line and kill the flush_tlb_local and flush_tlb_global exports.
>     Also there is just a single modular users in SVM, I wonder if there is
>     any way to get rid of that one as well.
> 
> Also I think cpu_tlbstate itself could be marked static in tlb.c with
> a few more changes, I wonder if would be worth it?
> 

For Address Space Isolation (ASI), I was planning on storing the ASI session
into cpu_tlbstate (https://lkml.org/lkml/2020/2/26/699) as the ASI session
then provides the TLB flushing information based on the ASI used. In that case,
I would need cpu_tlbstate to be non-static. Otherwise I can have my own percpu
asi_session structures, but using cpu_tlbstate seemed more appropriate to me.
This is opened for discussion; for now, I am waiting for more changes that tglx
is making, before rebasing ASI.

alex.