From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752743AbbCQHkl (ORCPT ); Tue, 17 Mar 2015 03:40:41 -0400 Received: from mail.skyhub.de ([78.46.96.112]:60053 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752392AbbCQHke (ORCPT ); Tue, 17 Mar 2015 03:40:34 -0400 Date: Tue, 17 Mar 2015 08:39:01 +0100 From: Borislav Petkov To: Ingo Molnar Cc: Denys Vlasenko , linux-tip-commits@vger.kernel.org, linux-kernel@vger.kernel.org, keescook@chromium.org, ast@plumgrid.com, fweisbec@gmail.com, oleg@redhat.com, tglx@linutronix.de, torvalds@linux-foundation.org, hpa@zytor.com, wad@chromium.org, rostedt@goodmis.org Subject: Re: [tip:x86/asm] x86/asm/entry/64: Remove unused thread_struct::usersp Message-ID: <20150317073901.GC19645@pd.tnic> References: <1425984307-2143-2-git-send-email-dvlasenk@redhat.com> <20150316164707.GB23015@pd.tnic> <55075736.7030003@redhat.com> <20150317070830.GA19645@pd.tnic> <20150317071316.GA22758@gmail.com> <20150317072118.GA26864@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20150317072118.GA26864@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 17, 2015 at 08:21:18AM +0100, Ingo Molnar wrote: > Assuming this does not fix the regression, could you apply the minimal > patch below - which reverts the old_rsp handling change. > > (The rest of the commit are in a third patch, but those are only > comment changes.) > > So my theory is that this change is what will revert the regression. Yep, it does. Below is the diff that works (it is the rough revert without the comments :-)): --- diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 66a1954439ea..e39bf83cb55b 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -496,6 +496,7 @@ struct thread_struct { #ifdef CONFIG_X86_32 unsigned long sysenter_cs; #else + unsigned long usersp; /* Copy from PDA */ unsigned short es; unsigned short ds; unsigned short fsindex; @@ -907,6 +908,11 @@ extern unsigned long thread_saved_pc(struct task_struct *tsk); #define task_pt_regs(tsk) ((struct pt_regs *)(tsk)->thread.sp0 - 1) extern unsigned long KSTK_ESP(struct task_struct *task); +/* + * User space RSP while inside the SYSCALL fast path + */ +DECLARE_PER_CPU(unsigned long, old_rsp); + #endif /* CONFIG_X86_64 */ extern void start_thread(struct pt_regs *regs, unsigned long new_ip, diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 14df2be4711f..e8c124a1f885 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -161,6 +161,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, p->thread.sp0 = (unsigned long)task_stack_page(p) + THREAD_SIZE; childregs = task_pt_regs(p); p->thread.sp = (unsigned long) childregs; + p->thread.usersp = me->thread.usersp; set_tsk_thread_flag(p, TIF_FORK); p->thread.io_bitmap_ptr = NULL; @@ -234,8 +235,10 @@ start_thread_common(struct pt_regs *regs, unsigned long new_ip, loadsegment(es, _ds); loadsegment(ds, _ds); load_gs_index(0); + current->thread.usersp = new_sp; regs->ip = new_ip; regs->sp = new_sp; + this_cpu_write(old_rsp, new_sp); regs->cs = _cs; regs->ss = _ss; regs->flags = X86_EFLAGS_IF; @@ -395,6 +398,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) /* * Switch the PDA and FPU contexts. */ + prev->usersp = this_cpu_read(old_rsp); + this_cpu_write(old_rsp, next->usersp); this_cpu_write(current_task, next_p); /* -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. --