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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=unavailable 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 0A69BC433ED for ; Wed, 19 May 2021 19:13:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D42DF6108D for ; Wed, 19 May 2021 19:13:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230391AbhESTOd (ORCPT ); Wed, 19 May 2021 15:14:33 -0400 Received: from mx2.suse.de ([195.135.220.15]:47110 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229505AbhESTOb (ORCPT ); Wed, 19 May 2021 15:14:31 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 88F15AFAB; Wed, 19 May 2021 19:13:10 +0000 (UTC) Date: Wed, 19 May 2021 21:13:08 +0200 From: Joerg Roedel To: Peter Zijlstra Cc: Joerg Roedel , x86@kernel.org, Hyunwook Baek , hpa@zytor.com, Andy Lutomirski , Dave Hansen , Jiri Slaby , Dan Williams , Tom Lendacky , Juergen Gross , Kees Cook , David Rientjes , Cfir Cohen , Erdem Aktas , Masami Hiramatsu , Mike Stunes , Sean Christopherson , Martin Radev , Arvind Sankar , linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v2 5/8] x86/sev-es: Leave NMI-mode before sending signals Message-ID: References: <20210519135251.30093-1-joro@8bytes.org> <20210519135251.30093-6-joro@8bytes.org> <20210519175450.GF21560@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210519175450.GF21560@worktop.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, thanks for your review. On Wed, May 19, 2021 at 07:54:50PM +0200, Peter Zijlstra wrote: > On Wed, May 19, 2021 at 03:52:48PM +0200, Joerg Roedel wrote: > > --- a/arch/x86/kernel/sev.c > > +++ b/arch/x86/kernel/sev.c > > @@ -1343,9 +1343,10 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) > > return; > > } > > > > + instrumentation_begin(); > > + > > irq_state = irqentry_nmi_enter(regs); > > lockdep_assert_irqs_disabled(); > > - instrumentation_begin(); > > > > /* > > * This is invoked through an interrupt gate, so IRQs are disabled. The > > That's just plain wrong. No instrumentation is allowed before you enter > the exception context. Okay. > > + irqentry_nmi_exit(regs, irq_state); > > + > > And this is wrong too; because at this point the handler doesn't run in > _any_ context anymore, certainly not one you can call regular C code > from. The #VC handler is at this point not running on the IST stack anymore, but on the stack it came from or on the task stack. So my believe was that at this point it inherits the context it came from (just like the page-fault handler). But I also don't fully understand the context tracking, so is my assumption wrong? Regards, Joerg