Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757067AbbDXPaU (ORCPT ); Fri, 24 Apr 2015 11:30:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54520 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752801AbbDXPaR (ORCPT ); Fri, 24 Apr 2015 11:30:17 -0400 Message-ID: <553A6166.4050104@redhat.com> Date: Fri, 24 Apr 2015 17:29:42 +0200 From: Denys Vlasenko User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Andy Lutomirski CC: Steven Rostedt , Linus Torvalds , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Oleg Nesterov , Frederic Weisbecker , Alexei Starovoitov , Will Drewry , Kees Cook , X86 ML , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/2] x86: stop using PER_CPU_VAR(kernel_stack) References: <1426970678-600-1-git-send-email-dvlasenk@redhat.com> <20150323101815.35bd61c7@gandalf.local.home> <551048E9.6060800@redhat.com> <20150323132847.79e18ea5@grimm.local.home> <55104F81.8050803@redhat.com> <20150323134510.2a04e387@gandalf.local.home> <5510528F.7050507@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2468 Lines: 78 On 03/23/2015 07:27 PM, Andy Lutomirski wrote: > On Mon, Mar 23, 2015 at 10:51 AM, Denys Vlasenko wrote: >> On 03/23/2015 06:45 PM, Steven Rostedt wrote: >>> On Mon, 23 Mar 2015 18:38:09 +0100 >>> Denys Vlasenko wrote: >>> >>>>> Can we do a: >>>>> >>>>> #define cpu_current_top_of_stack (cpu_tss + TSS_sp0) >>>> >>>> We already do something similar: >>>> >>>> static inline unsigned long current_top_of_stack(void) >>>> { >>>> #ifdef CONFIG_X86_64 >>>> return this_cpu_read_stable(cpu_tss.x86_tss.sp0); >>>> #else >>>> /* sp0 on x86_32 is special in and around vm86 mode. */ >>>> return this_cpu_read_stable(cpu_current_top_of_stack); >>>> #endif >>>> } >>> >>> So can we then have: >>> >>> #ifdef __ASSEMBLY__ >>> # define cpu_current_top_of_stack (cpu_tss + TSS_sp0) >>> #else >>> # define cpu_current_top_of_stack (cpu_tss.x86_tss.sp0) >>> #endif >>> >>> And get rid of that if statement in the static inline? >> >> I prefer less macro indirection in assembly code, >> but I won't object too strongly if this would be done. >> >> It's up to other x86 maintainers to agree - I'm touching >> the code recently changed by Andy, he may see the way forward >> somewhat differently. >> > > I kind of like Steven's idea. Although.. shouldn't we go all the way and do: > > #ifdef __ASSEMBLY__ > #ifdef CONFIG_X86_64 > #define cpu_current_top_of_stack %gs:(cpu_tss + TSS_sp0) > #else > #define cpu_current_top_of_stack %gs:(current_top_of_stack) > #endif > #endif Which .h file do you propose to have this in? processor.h is not suitable, it is not __ASSEMBLY__-fied. I'm looking at a place where to put it. For example, one of the users of the (cpu_tss + TSS_sp0) expression, xen-asm_64.S, has only these few includes: #include #include #include #include #include #include #include "xen-asm.h" None seems suitable. I will probably have to include thread_info.h too, and put the define there. Ugly ugly ugly. I'll resend a patchset where a new patch #3 attempts to do this "unification". I personally don't see it as a clear improvement. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/