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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 97206C282D9 for ; Thu, 31 Jan 2019 08:56:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 622C12087F for ; Thu, 31 Jan 2019 08:56:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730690AbfAaI4K (ORCPT ); Thu, 31 Jan 2019 03:56:10 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:39606 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726217AbfAaI4J (ORCPT ); Thu, 31 Jan 2019 03:56:09 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 53C75A78; Thu, 31 Jan 2019 00:56:09 -0800 (PST) Received: from [10.1.197.45] (e112298-lin.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5D6FF3F589; Thu, 31 Jan 2019 00:56:06 -0800 (PST) Subject: Re: [PATCH v9 01/26] arm64: Fix HCR.TGE status for NMI contexts To: Christoffer Dall Cc: James Morse , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, daniel.thompson@linaro.org, joel@joelfernandes.org, marc.zyngier@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, mark.rutland@arm.com, Arnd Bergmann , linux-arch@vger.kernel.org, stable@vger.kernel.org References: <1548084825-8803-1-git-send-email-julien.thierry@arm.com> <1548084825-8803-2-git-send-email-julien.thierry@arm.com> <8e8c4f5b-5b83-7bbc-1b84-36d68e210968@arm.com> <847c54ef-ea41-eea5-8aff-72e0cea465f8@arm.com> <20190131081900.GM13482@e113682-lin.lund.arm.com> From: Julien Thierry Message-ID: <32af4a5c-7aeb-0171-1b4a-2cbee5f78bca@arm.com> Date: Thu, 31 Jan 2019 08:56:04 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20190131081900.GM13482@e113682-lin.lund.arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 31/01/2019 08:19, Christoffer Dall wrote: > On Mon, Jan 28, 2019 at 03:42:42PM +0000, Julien Thierry wrote: >> Hi James, >> >> On 28/01/2019 11:48, James Morse wrote: >>> Hi Julien, >>> >>> On 21/01/2019 15:33, Julien Thierry wrote: >>>> When using VHE, the host needs to clear HCR_EL2.TGE bit in order >>>> to interract with guest TLBs, switching from EL2&0 translation regime >>> >>> (interact) >>> >>> >>>> to EL1&0. >>>> >>>> However, some non-maskable asynchronous event could happen while TGE is >>>> cleared like SDEI. Because of this address translation operations >>>> relying on EL2&0 translation regime could fail (tlb invalidation, >>>> userspace access, ...). >>>> >>>> Fix this by properly setting HCR_EL2.TGE when entering NMI context and >>>> clear it if necessary when returning to the interrupted context. >>> >>> Yes please. This would not have been fun to debug! >>> >>> Reviewed-by: James Morse >>> >>> >> >> Thanks. >> >>> >>> I was looking for why we need core code to do this, instead of updating the >>> arch's call sites. Your 'irqdesc: Add domain handlers for NMIs' patch (pointed >>> to from the cover letter) is the reason: core-code calls nmi_enter()/nmi_exit() >>> itself. >>> >> >> Yes, that's the main reason. >> > I wondered the same thing, but I don't understand the explanation :( > > Why can't we do a local_daif_mask() around the (very small) calls that > clear TGE instead? > That would protect against the pseudo-NMIs, but you can still get an SDEI at that point even with all daif bits set. Or did I misunderstand how SDEI works? Thanks, -- Julien Thierry