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=-5.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 1B3EEC43467 for ; Tue, 13 Oct 2020 11:53:54 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 BFC1B2080A for ; Tue, 13 Oct 2020 11:53:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="pGcqkxYD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BFC1B2080A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+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=merlin.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:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Oz7r3pWp70Z6npLr91E4bNnP1WONuVpQc91B09vexrU=; b=pGcqkxYDHxyubx8TIxPCTDo8A WRNXBifwnx7aM7Wfa807FlnjeAUY/A2gKKQL5WRzmC8RHs36DQkV91x1Hyv2DxU/VIwKp6UEAmrrM pkQZYmqqeiwACRXu+mLmEelVlHq8EiwURPQKXlUAPxpxfDwvPghp/25I1mULoAEYtlmvCHqcINM9O uKuqxCt0easpN+XnItSFVWH9avu+3/YBA2dbACDUkrriblBPuBRlk/cGcUwF44uaTso14rBa9HaKL ++9gCKilWpvZUvxXA6c7PR9Jj7n9u8U/zVj7RF0IRTTqW2IpCDLodmYNIbHJl1YcsAkE2mW9sLjER J1JQ/cruA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kSIqy-0006pP-SW; Tue, 13 Oct 2020 11:52:28 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kSIqv-0006oe-Px for linux-arm-kernel@lists.infradead.org; Tue, 13 Oct 2020 11:52:26 +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 DBD6D1FB; Tue, 13 Oct 2020 04:52:22 -0700 (PDT) Received: from [172.16.1.113] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3EA933F719; Tue, 13 Oct 2020 04:52:21 -0700 (PDT) Subject: Re: [RFC PATCH 1/3] arm64: kvm: Handle Asymmetric AArch32 systems To: Marc Zyngier References: <20201008181641.32767-1-qais.yousef@arm.com> <20201008181641.32767-2-qais.yousef@arm.com> <7c058d22dce84ec7636863c1486b11d1@kernel.org> <20201009095857.cq3bmmobxeq3tm5z@e107158-lin.cambridge.arm.com> <63e379d1399b5c898828f6802ce3dca5@kernel.org> <20201009124817.i7u53qrntvu7l5zq@e107158-lin.cambridge.arm.com> <54379ee1-97b1-699b-9500-655164f2e083@arm.com> <8cdbcf81bae94f4b030e2906191d80af@kernel.org> From: James Morse Message-ID: <13eb5d05-9eaf-7640-cd44-cfd7f8820257@arm.com> Date: Tue, 13 Oct 2020 12:51:37 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <8cdbcf81bae94f4b030e2906191d80af@kernel.org> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201013_075225_911913_65FE25D6 X-CRM114-Status: GOOD ( 18.37 ) 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: linux-arch@vger.kernel.org, "Peter Zijlstra \(Intel\)" , Greg Kroah-Hartman , Morten Rasmussen , Linus Torvalds , Catalin Marinas , Will Deacon , Qais Yousef , 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+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Marc, On 13/10/2020 11:32, Marc Zyngier wrote: > On 2020-10-12 16:32, James Morse wrote: >> On 09/10/2020 13:48, Qais Yousef wrote: >>> On 10/09/20 13:34, Marc Zyngier wrote: >>>> You can try setting vcpu->arch.target to -1, which is already caught by >>>> kvm_vcpu_initialized() right at the top of this function. This will >> >>>> prevent any reentry unless the VMM issues a KVM_ARM_VCPU_INIT ioctl. >> >> This doesn't reset SPSR, so this lets the VMM restart the guest with a >> bad value. > > That's not my reading of the code. Without a valid target, you cannot enter > the guest (kvm_vcpu_initialized() prevents you to do so). To set the target, > you need to issue a KVM_ARM_VCPU_INIT ioctl, which eventually calls > kvm_reset_vcpu(), which does set PSTATE to something legal. aha! So it does, this is what I was missing. > Or do you mean the guest's SPSR_EL1? Why would that matter? > >> I think we should make it impossible to return to aarch32 from EL2 on >> these systems. > > And I'm saying that the above fulfills that requirement. Am I missing > something obvious? Nope, I was. I agree the check on entry from user-space isn't needed. Thanks, James _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel