From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751493AbcBJOvZ (ORCPT ); Wed, 10 Feb 2016 09:51:25 -0500 Received: from mail.skyhub.de ([78.46.96.112]:52558 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750761AbcBJOvX (ORCPT ); Wed, 10 Feb 2016 09:51:23 -0500 Date: Wed, 10 Feb 2016 15:51:16 +0100 From: Borislav Petkov To: Michael Matz , luto@amacapital.net Cc: mingo@kernel.org, tglx@linutronix.de, oleg@redhat.com, brgerst@gmail.com, mcgrof@suse.com, dave.hansen@linux.intel.com, akpm@linux-foundation.org, dvlasenk@redhat.com, peterz@infradead.org, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, toshi.kani@hp.com, luto@kernel.org, aryabinin@virtuozzo.com, hpa@zytor.com, linux-tip-commits@vger.kernel.org Subject: [PATCH -v1.1] x86/mm: Fix INVPCID asm constraint Message-ID: <20160210145116.GF23914@pd.tnic> References: <8a62b23ad686888cee01da134c91409e22064db9.1454096309.git.luto@kernel.org> <20160210120827.GA11832@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 10, 2016 at 02:48:02PM +0100, Michael Matz wrote: > Hi, > > On Wed, 10 Feb 2016, Borislav Petkov wrote: > > > --- a/arch/x86/include/asm/tlbflush.h > > +++ b/arch/x86/include/asm/tlbflush.h > > @@ -23,7 +23,7 @@ static inline void __invpcid(unsigned long pcid, unsigned long addr, > > * invpcid (%rcx), %rax in long mode. > > */ > > asm volatile (".byte 0x66, 0x0f, 0x38, 0x82, 0x01" > > - : : "m" (desc), "a" (type), "c" (desc) : "memory"); > > + : : "m" (*desc), "a" (type), "c" (desc) : "memory"); > > That still doesn't do what you want. Arrays in C are funny. *desc is > exactly equivalent to desc[0], _not_ to the whole array, Doh! > indeed there's no C syntax to name an lvalue of array type in normal > expressions. You need to jump through hoops for this: > > "m" (*(struct {unsigned long x[2];} *)desc) Aha! That's why we wrapped the array in clwb() in a struct too, btw: static inline void clwb(volatile void *__p) { volatile struct { char x[64]; } *p = __p; ... > It'd probably be easier to simply declare the descriptor as a struct, > rather than an array, then the original syntax would have been mostly > correct: > > struct {u64 d[2];} desc = { pcid, addr }; > asm ... "m" (desc), "c" (&desc) Sounds better. Done. How does that below look like? Thanks Micha! --- From: Borislav Petkov Date: Wed, 10 Feb 2016 12:53:48 +0100 Subject: [PATCH -v1.1] x86/mm: Fix INVPCID asm constraint MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit So we want to specify the dependency on both @pcid and @addr so that the compiler doesn't reorder accesses to them *before* the TLB flush. But for that to work, we need to express this properly in the inline asm and deref the whole desc array, not the pointer to it. See clwb() for an example. This fixes the build error on 32-bit: arch/x86/include/asm/tlbflush.h: In function ‘__invpcid’: arch/x86/include/asm/tlbflush.h:26:18: error: memory input 0 is not directly addressable which gcc4.7 caught but 5.x didn't. Which is strange. :-\ Signed-off-by: Borislav Petkov Cc: Andrew Morton Cc: Andrey Ryabinin Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Ingo Molnar Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Michael Matz Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Toshi Kani Cc: linux-mm@kvack.org --- arch/x86/include/asm/tlbflush.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index 6f9e27aa2aaf..c24b4224d439 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -11,7 +11,7 @@ static inline void __invpcid(unsigned long pcid, unsigned long addr, unsigned long type) { - u64 desc[2] = { pcid, addr }; + struct { u64 d[2]; } desc = { { pcid, addr } }; /* * The memory clobber is because the whole point is to invalidate @@ -23,7 +23,7 @@ static inline void __invpcid(unsigned long pcid, unsigned long addr, * invpcid (%rcx), %rax in long mode. */ asm volatile (".byte 0x66, 0x0f, 0x38, 0x82, 0x01" - : : "m" (desc), "a" (type), "c" (desc) : "memory"); + : : "m" (desc), "a" (type), "c" (&desc) : "memory"); } #define INVPCID_TYPE_INDIV_ADDR 0 -- 2.3.5 -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply.