From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752860AbbCQHwA (ORCPT ); Tue, 17 Mar 2015 03:52:00 -0400 Received: from mail-wi0-f175.google.com ([209.85.212.175]:37444 "EHLO mail-wi0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752653AbbCQHvp (ORCPT ); Tue, 17 Mar 2015 03:51:45 -0400 Date: Tue, 17 Mar 2015 08:51:39 +0100 From: Ingo Molnar To: Borislav Petkov 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: <20150317075139.GA27898@gmail.com> 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=us-ascii 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 * Ingo Molnar wrote: > Assuming this does not fix the regression, could you apply the > minimal patch below - which reverts the old_rsp handling change. Assuming this solves the regression (it really should, it's now equivalent to a full revert minus comments): > @@ -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); > > /* can you confirm that your guest (sometimes) uses SYSENTER to do syscalls? If yes then my theory is that we broke SYSENTER (or SYSEXIT) support - and that this would not be visible in our normal tests of KVM because SYSCALL is used most of the time. Thanks, Ingo