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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 EAA8FC76195 for ; Mon, 15 Jul 2019 13:48:59 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BAD872081C for ; Mon, 15 Jul 2019 13:48:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="dgiGGg38" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BAD872081C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=I+3K6RZfEFUeV+ZtqYKuJCOPlNMJWdK9XKjeqwwEoHc=; b=dgiGGg38/Dj7Q2 4uVkhjOnqsYWAJCJB0Ff5KT/V44Bh1NprWMNI7VtEcRosvuqhWwRX/5Nd3VSEuGWDXGUvD4ajFDE1 Dpk7qQs86ItkGOhSTKxZGCTbPpICSrBDfBx2Y+Xh9lOrhj5d+gy2xvt1L7GRzwLYWyQNv2356njVy 0/yZegByQx1nvJf0/SeCq/Bib2Xv3PlTihniwQc3VBH+3LWKFr4tsmFVeosJ/2/chcpK12X5FQRGT jEBJeZd1OewCgQ24mClPw5Stfa6+SZ3yzOyPkSkkHMckNasuiPixc/4ne6q9gtJYATRWoupg28lQ3 wsT3Q9bofPeM+1U1HdxA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hn1Lc-00027E-Mu; Mon, 15 Jul 2019 13:48:56 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hn1LZ-00025E-EW for linux-arm-kernel@lists.infradead.org; Mon, 15 Jul 2019 13:48:54 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6DBAA28; Mon, 15 Jul 2019 06:48:52 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 697233F71F; Mon, 15 Jul 2019 06:48:51 -0700 (PDT) Date: Mon, 15 Jul 2019 14:48:49 +0100 From: Mark Rutland To: Dave Martin Subject: Re: [RFC] Add virtual SDEI support in qemu Message-ID: <20190715134848.GI56232@lakrids.cambridge.arm.com> References: <1b0aa6b2-80b1-a72e-6849-7323c3b9c6bc@huawei.com> <20190715134059.GJ2790@e103592.cambridge.arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190715134059.GJ2790@e103592.cambridge.arm.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190715_064853_536493_153F8FEC X-CRM114-Status: GOOD ( 21.31 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marc Zyngier , qemu-devel@nongnu.org, qemu-arm@nongnu.org, Guoheyi , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Jul 15, 2019 at 02:41:00PM +0100, Dave Martin wrote: > On Sat, Jul 13, 2019 at 05:53:57PM +0800, Guoheyi wrote: > > Hi folks, > > > > Do it make sense to implement virtual SDEI in qemu? So that we can have the > > standard way for guest to handle NMI watchdog, RAS events and something else > > which involves SDEI in a physical ARM64 machine. > > > > My basic idea is like below: > > > > 1. Change a few lines of code in kvm to allow unhandled SMC invocations > > (like SDEI) to be sent to qemu, with exit reason of KVM_EXIT_HYPERCALL, so > > we don't need to add new API. > > So long as KVM_EXIT_HYPERCALL reports sufficient information so that > userspace can identify the cause as an SMC and retrieve the SMC > immediate field, this seems feasible. > > For its own SMCCC APIs, KVM exclusively uses HVC, so rerouting SMC to > userspace shouldn't conflict. Be _very_ careful here! In systems without EL3 (and without NV), SMC UNDEFs rather than trapping to EL2. Given that, we shouldn't build a hypervisor ABI that depends on SMC. I am strongly of the opinion that (for !NV) we should always use HVC here and have KVM appropriately forward calls to userspace, rather than trying to use HVC/SMC to distinguish handled-by-kernel and handled-by-userspace events. For NV, the first guest hypervisor would use SMC to talk to KVM, all else being the same. > This bouncing of SMCs to userspace would need to be opt-in, otherwise > old userspace would see exits that it doesn't know what to do with. > > > 2. qemu handles supported SDEI calls just as the spec says for what a > > hypervisor should do for a guest OS. > > > > 3. For interrupts bound to hypervisor, qemu should stop injecting the IRQ to > > guest through KVM, but jump to the registered event handler directly, > > including context saving and restoring. Some interrupts like virtual timer > > are handled by kvm directly, so we may refuse to bind such interrupts to > > SDEI events. > > Something like that. > > Interactions between SDEI and PSCI would need some thought: for example, > after PSCI_CPU_ON, the newly online cpu needs to have SDEs masked. > > One option (suggested to me by James Morse) would be to allow userspace > to disable in the in-kernel PSCI implementation and provide its own > PSCI to the guest via SMC -- in which case userspace that wants to > implement SDEI would have to implement PSCI as well. I think this would be the best approach, since it puts userspace in charge of everything. However, this interacts poorly with FW-based mitigations that we implement in hyp. I suspect we'd probably need a mechanism to delegate that responsibility back to the kernel, and figure out if that has any interaction with thigns that got punted to userspace... Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel