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Message-ID: <20180419003833.GO6694@tassilo.jf.intel.com>
Date: Wed, 18 Apr 2018 17:38:33 -0700
From: Andi Kleen <ak@...ux.intel.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Joerg Roedel <joro@...tes.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>,
"H . Peter Anvin" <hpa@...or.com>,
the arch/x86 maintainers <x86@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-mm <linux-mm@...ck.org>, Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...el.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Juergen Gross <jgross@...e.com>,
Peter Zijlstra <peterz@...radead.org>,
Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Brian Gerst <brgerst@...il.com>,
David Laight <David.Laight@...lab.com>,
Denys Vlasenko <dvlasenk@...hat.com>,
Eduardo Valentin <eduval@...zon.com>,
Greg KH <gregkh@...uxfoundation.org>,
Will Deacon <will.deacon@....com>,
"Liguori, Anthony" <aliguori@...zon.com>,
Daniel Gruss <daniel.gruss@...k.tugraz.at>,
Hugh Dickins <hughd@...gle.com>,
Kees Cook <keescook@...gle.com>,
Andrea Arcangeli <aarcange@...hat.com>, Waim@...ux.intel.com
Subject: Re: [PATCH 03/35] x86/entry/32: Load task stack from x86_tss.sp1 in
SYSENTER handler
On Wed, Apr 18, 2018 at 05:02:02PM -0700, Linus Torvalds wrote:
> On Wed, Apr 18, 2018 at 4:26 PM, Andi Kleen <ak@...ux.intel.com> wrote:
> >
> > Seems like a hack. Why can't that be stored in a per cpu variable?
>
> It *is* a percpu variable - the whole x86_tss structure is percpu.
>
> I guess it could be a different (separate) percpu variable, but might
> as well use the space we already have allocated.
Would be better/cleaner to use a separate variable instead of reusing
x86 structures like this. Who knows what subtle side effects that
may have eventually.
It will be also easier to understand in the code.
-Andi
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