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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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