linux-kernel - Re: [PATCH 1/2] x86/mm/kaiser: Remove unused user-mapped page-aligned section

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Date:   Tue, 28 Nov 2017 13:43:13 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>, daniel.gruss@...k.tugraz.at,
        hughd@...gle.com, keescook@...gle.com, linux-mm@...ck.org,
        michael.schwarz@...k.tugraz.at, moritz.lipp@...k.tugraz.at,
        richard.fellner@...dent.tugraz.at
Subject: Re: [PATCH 1/2] x86/mm/kaiser: Remove unused user-mapped
 page-aligned section

On Tue, Nov 28, 2017 at 10:20:25AM +0100, Peter Zijlstra wrote:
> On Mon, Nov 27, 2017 at 10:10:12PM -0600, Josh Poimboeuf wrote:
> > The '.data..percpu..user_mapped..page_aligned' section isn't used
> > anywhere.  Remove it and its related macros.
> 
> With my patches:
> 
>   arch/x86/events/intel/ds.c:DEFINE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(struct debug_store, cpu_debug_store);
> 
> is the only user left of any of that.
> 
> I suppose we could just allocate a whole page for that and use
> kaiser_add_mapping() for it. Then we can remove all of
> DEFINE_.*_USER_MAPPED().

Or we could field it a spot in the cpu_entry_area I suppose.