From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1890FC2D0EF for ; Sat, 18 Apr 2020 10:00:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E3B6821D82 for ; Sat, 18 Apr 2020 10:00:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725949AbgDRKAE (ORCPT ); Sat, 18 Apr 2020 06:00:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46240 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1725857AbgDRKAD (ORCPT ); Sat, 18 Apr 2020 06:00:03 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7BBCAC061A0C for ; Sat, 18 Apr 2020 03:00:03 -0700 (PDT) Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jPkGL-0006nT-Ir; Sat, 18 Apr 2020 11:59:49 +0200 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id E863B101304; Sat, 18 Apr 2020 11:59:48 +0200 (CEST) From: Thomas Gleixner To: "Singh\, Balbir" , "linux-kernel\@vger.kernel.org" Cc: "keescook\@chromium.org" , "tony.luck\@intel.com" , "benh\@kernel.crashing.org" , "jpoimboe\@redhat.com" , "x86\@kernel.org" , "dave.hansen\@intel.com" Subject: Re: [PATCH v3 3/5] arch/x86/mm: Refactor cond_ibpb() to support other use cases In-Reply-To: <12023cc73a6344ed7499e09492a6934c1dfaf044.camel@amazon.com> References: <20200408090229.16467-1-sblbir@amazon.com> <20200408090229.16467-4-sblbir@amazon.com> <87sgh2l0q4.fsf@nanos.tec.linutronix.de> <12023cc73a6344ed7499e09492a6934c1dfaf044.camel@amazon.com> Date: Sat, 18 Apr 2020 11:59:48 +0200 Message-ID: <87pnc5xgff.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Singh, Balbir" writes: > On Fri, 2020-04-17 at 15:07 +0200, Thomas Gleixner wrote: >> >> Balbir Singh writes: >> > >> > /* >> > - * Use bit 0 to mangle the TIF_SPEC_IB state into the mm pointer which is >> > - * stored in cpu_tlb_state.last_user_mm_ibpb. >> > + * Bits to mangle the TIF_SPEC_IB state into the mm pointer which is >> > + * stored in cpu_tlb_state.last_user_mm_spec. >> > */ >> > #define LAST_USER_MM_IBPB 0x1UL >> > +#define LAST_USER_MM_SPEC_MASK (LAST_USER_MM_IBPB) >> > >> > /* Reinitialize tlbstate. */ >> > - this_cpu_write(cpu_tlbstate.last_user_mm_ibpb, LAST_USER_MM_IBPB); >> > + this_cpu_write(cpu_tlbstate.last_user_mm_spec, LAST_USER_MM_IBPB); >> >> Shouldn't that be LAST_USER_MM_MASK? >> > No, that crashes the system for SW flushes, because it tries to flush the L1D > via the software loop and early enough we don't have the l1d_flush_pages > allocated. LAST_USER_MM_MASK has LAST_USER_MM_FLUSH_L1D bit set. You can trivially prevent this by checking l1d_flush_pages != NULL. Thanks, tglx