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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 58ED9C2D0EA for ; Wed, 8 Apr 2020 11:16:09 +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 1017520753 for ; Wed, 8 Apr 2020 11:16:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="idmKGZSu" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1017520753 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: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=rldvGC18f0eYvoqV4u/NkAqtHvrKcFdqR18CfFmuhyQ=; b=idmKGZSu/WguVa tBsyN/PPbOOgDsfgW6ZaA6tstvKouF7dN02ruU73cB1ctLR3dtnQVYxMe8J5TqCsAZPWropFAZZcS HPMkSmlAKObBTZbvfQQcKIfoZEzay4gX9/K69GlFI15pHlBDERmyaOqvgKtTTeUTQCiF1UV5Vgeyz Y0MbgEX63U6JkyIdMJPa6vKSf1bazOFdBT2Hc6rR1gaMP+AwDi68Db+xw91014wlCKwWIfpIskPaj I7BBVdlP8yhfrzzOOTHR5hBQhKjjl5Wd2OKMvO0i1YNEKJdK+PAzbShXx2n/w+cpPIpAci2u3YcsA ZK/CBLvXtLyCiiem/ikw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jM8gi-0008NQ-Fu; Wed, 08 Apr 2020 11:16:08 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jM8ge-0008N0-MD for linux-arm-kernel@lists.infradead.org; Wed, 08 Apr 2020 11:16:06 +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 BA07731B; Wed, 8 Apr 2020 04:16:03 -0700 (PDT) Received: from [192.168.0.14] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E1E153F73D; Wed, 8 Apr 2020 04:16:02 -0700 (PDT) Subject: Re: [PATCH] KVM: arm64: arch_timer shouldn't assume the vcpu is loaded To: Marc Zyngier References: <20200406150355.4859-1-james.morse@arm.com> <20200408110726.4d81bc3b@why> From: James Morse Message-ID: Date: Wed, 8 Apr 2020 12:16:01 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200408110726.4d81bc3b@why> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200408_041604_810385_BC2DEE7B X-CRM114-Status: GOOD ( 21.45 ) 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: Andre Przywara , Julien Thierry , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, Suzuki K Poulose 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 Hi Marc, On 08/04/2020 11:07, Marc Zyngier wrote: > On Mon, 6 Apr 2020 16:03:55 +0100 > James Morse wrote: > >> kvm_arch_timer_get_input_level() needs to get the arch_timer_context for >> a particular vcpu, and uses kvm_get_running_vcpu() to find it. >> >> kvm_arch_timer_get_input_level() may be called to handle a user-space >> write to the redistributor, where the vcpu is not loaded. This causes >> kvm_get_running_vcpu() to return NULL: >> | Unable to handle kernel paging request at virtual address 0000000000001ec0 >> | Mem abort info: >> | ESR = 0x96000004 >> | EC = 0x25: DABT (current EL), IL = 32 bits >> | SET = 0, FnV = 0 >> | EA = 0, S1PTW = 0 >> | Data abort info: >> | ISV = 0, ISS = 0x00000004 >> | CM = 0, WnR = 0 >> | user pgtable: 4k pages, 48-bit VAs, pgdp=000000003cbf9000 >> | [0000000000001ec0] pgd=0000000000000000 >> | Internal error: Oops: 96000004 [#1] PREEMPT SMP >> | Modules linked in: r8169 realtek efivarfs ip_tables x_tables >> | CPU: 1 PID: 2615 Comm: qemu-system-aar Not tainted 5.6.0-rc7 #30 >> | Hardware name: Marvell mvebu_armada-37xx/mvebu_armada-37xx, BIOS 2018.03-devel-18.12.3-gc9aa92c-armbian 02/20/2019 >> | pstate: 00000085 (nzcv daIf -PAN -UAO) >> | pc : kvm_arch_timer_get_input_level+0x1c/0x68 >> | lr : kvm_arch_timer_get_input_level+0x1c/0x68 >> >> | Call trace: >> | kvm_arch_timer_get_input_level+0x1c/0x68 >> | vgic_get_phys_line_level+0x3c/0x90 >> | vgic_mmio_write_senable+0xe4/0x130 >> | vgic_uaccess+0xe0/0x100 >> | vgic_v3_redist_uaccess+0x5c/0x80 >> | vgic_v3_attr_regs_access+0xf0/0x200 >> | nvgic_v3_set_attr+0x234/0x250 >> | kvm_device_ioctl_attr+0xa4/0xf8 >> | kvm_device_ioctl+0x7c/0xc0 >> | ksys_ioctl+0x1fc/0xc18 >> | __arm64_sys_ioctl+0x24/0x30 >> | do_el0_svc+0x7c/0x148 >> | el0_sync_handler+0x138/0x258 >> | el0_sync+0x140/0x180 >> | Code: 910003fd f9000bf3 2a0003f3 97ff650c (b95ec001) >> | ---[ end trace 81287612d93f1e70 ]--- >> | note: qemu-system-aar[2615] exited with preempt_count 1 >> >> Loading the vcpu doesn't make a lot of sense for handling a device ioctl(), >> so instead pass the vcpu through to kvm_arch_timer_get_input_level(). Its >> not clear that an intid makes much sense without the paired vcpu. > > I don't fully agree with the analysis, Remember we are looking at the > state of the physical interrupt associated with a virtual interrupt, so > the vcpu doesn't quite make sense here if it isn't loaded. > > What does it mean to look at the HW timer when we are not in the right > context? For all we know, it is completely random (the only guarantee > we have is that it is disabled, actually). > My gut feeling is that this is another instance where we should provide > specific userspace accessors that would only deal with the virtual > state, and leave anything that deals with the physical state of the > interrupt to be exercised only by the guest. > Does it make sense? Broadly, yes. Specifically ... I'm not familiar enough with this code to work out where such a change should go! ~20 mins of grepping later~ Remove REGISTER_DESC_WITH_LENGTH() so that uaccess helpers have to be provided, and forbid NULL for the ur/uw values in REGISTER_DESC_WITH_BITS_PER_IRQ_SHARED()...? Or if that is too invasive, something like, (totally, untested): ----------------%<---------------- diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c index 97fb2a40e6ba..30ae5f29e429 100644 --- a/virt/kvm/arm/vgic/vgic-mmio.c +++ b/virt/kvm/arm/vgic/vgic-mmio.c @@ -113,10 +113,11 @@ void vgic_mmio_write_senable(struct kvm_vcpu *vcpu, struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i); raw_spin_lock_irqsave(&irq->irq_lock, flags); - if (vgic_irq_is_mapped_level(irq)) { + if (kvm_running_vcpu() && vgic_irq_is_mapped_level(irq)) { bool was_high = irq->line_level; /* + * Unless we are running due to a user-space access, * We need to update the state of the interrupt because * the guest might have changed the state of the device * while the interrupt was disabled at the VGIC level. ----------------%<---------------- Thanks, James _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel