linux-kernel - Re: [PATCH 2/8] x86/mm/cpa: Move flush_tlb

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Message-ID: <20180922103752.GI24124@hirez.programming.kicks-ass.net>
Date:   Sat, 22 Sep 2018 12:37:52 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
        x86@...nel.org, Bin Yang <bin.yang@...el.com>,
        Mark Gross <mark.gross@...el.com>
Subject: Re: [PATCH 2/8] x86/mm/cpa: Move flush_tlb_all()

On Fri, Sep 21, 2018 at 02:34:32PM -0700, Dave Hansen wrote:
> On 09/19/2018 01:50 AM, Peter Zijlstra wrote:
> > @@ -1528,28 +1538,8 @@ static int __change_page_attr(struct cpa
> >  	 * We have to split the large page:
> >  	 */
> >  	err = split_large_page(cpa, kpte, address);
> > -	if (!err) {
> ...
> > -		flush_tlb_all();
> > +	if (!err)
> >  		goto repeat;
> > -	}
> 
> I _think_ this is the only use of split_large_page()'s error code.  We
> can just make it return void now, right?

Then how does it decide to goto repeat or error out?

> BTW, I also really like doing the "final" TLB flush as close as possible
> to the actual PTE manipulation.  Makes it much less likely that we break it.

Yes.