From patchwork Mon Aug 13 14:57:38 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 10564477 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7DC641390 for ; Mon, 13 Aug 2018 15:54:19 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 6A3F9290DC for ; Mon, 13 Aug 2018 15:54:19 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5D388291C0; Mon, 13 Aug 2018 15:54:19 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI autolearn=unavailable version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 07B57290DC for ; Mon, 13 Aug 2018 15:54:19 +0000 (UTC) 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:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=hkzwD9mo9E1P0wg42sSPIgwk4FWTZlL0Kyi9CujgDxw=; b=cIGYZmfxW+SzqmBP1EKlDs/CHb JWhU+AJaF2Fso8+NOQkqjYVRhJ5WPFgwF5DM8UdswraclFWRwrX8A4EfW6kdswxco86fPFjkIVRd0 tTwZ5ulX9L3ttSTsuX8ZC49qwHeYPu84cx9qD8JMmu1ycTRrP54tJPXKnBZDCSYbaTuMqy2oexHqD NBpF9KpfNZSNb9kgbXiBfCvgsc6e1QgD+OTgpqm8gKP5PpUOaJddYi7+rv9KECDwkxs+cFW5NJbLo nQ6tLFb6cuEgfD9yuSdbncpDFErmBDqgDfmZUuMiQEl4A3k8/EildtstDDmuZMhdIasVZK89y6zPD KLvGCv+Q==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1fpFAa-0000I2-Pd; Mon, 13 Aug 2018 15:54:12 +0000 Received: from merlin.infradead.org ([2001:8b0:10b:1231::1]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1fpF9q-0007eD-AM for linux-arm-kernel@bombadil.infradead.org; Mon, 13 Aug 2018 15:53:26 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=References:In-Reply-To:Message-Id:Date: Subject:Cc:To:From:Sender:Reply-To:MIME-Version:Content-Type: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=Av9q8cQjITLi8u++m4Od+5LpCdAeZSzda5KYdZFWxxY=; b=Cy6hr+k54svl/5Vyd2MnHZmSu rIO9h7GbwF6Pj7pOxhpP0IbZZd/Bc/ZHecRDjV0MRNafxIcjd5zx2B98Lc59veL/4StrpB9MujHrr y0elxZUBBDuHUTRovoHGE6pit5eIsPzC3F4X5U+B31AKgpxK36n+2H0pqkuEq2obfHxcmcnlUM0Tq 5dzSTI2+8jTZuJC+HcBbc5uwRBDO/WJGDmRf1BaB1JZHhB32ejA97k3mv6uwYo0w4ShE0coZ3EGe+ NsAjB3BDdrqH1jEhQwH/W7K948nqvPWu1I4r6gjhcwUiwFHkfJJCFbbNWQ3Jm3dCzr3leGrqrMWJU yMmGCBQvw==; Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by merlin.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1fpEK1-0004Ul-NF for linux-arm-kernel@lists.infradead.org; Mon, 13 Aug 2018 14:59:55 +0000 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 8D92EED1; Mon, 13 Aug 2018 07:59:53 -0700 (PDT) Received: from approximate.Emea.Arm.com (approximate.Emea.Arm.com [10.4.13.119]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BFF443F5D0; Mon, 13 Aug 2018 07:59:50 -0700 (PDT) From: Marc Zyngier To: Paolo Bonzini , =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= Subject: [PATCH 20/37] KVM: arm/arm64: vgic: Let userspace opt-in to writable v2 IGROUPR Date: Mon, 13 Aug 2018 15:57:38 +0100 Message-Id: <20180813145755.16566-21-marc.zyngier@arm.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180813145755.16566-1-marc.zyngier@arm.com> References: <20180813145755.16566-1-marc.zyngier@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20180813_105954_047914_594EC97C X-CRM114-Status: GOOD ( 19.50 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Andrew Jones , Kees Cook , kvm@vger.kernel.org, "Gustavo A . R . Silva" , Andre Przywara , Punit Agrawal , Christoffer Dall , Dongjiu Geng , Jia He , Eric Auger , James Morse , Catalin Marinas , Suzuki Poulose , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP From: Christoffer Dall Simply letting IGROUPR be writable from userspace would break migration from old kernels to newer kernels, because old kernels incorrectly report interrupt groups as group 1. This would not be a big problem if userspace wrote GICD_IIDR as read from the kernel, because we could detect the incompatibility and return an error to userspace. Unfortunately, this is not the case with current userspace implementations and simply letting IGROUPR be writable from userspace for an emulated GICv2 silently breaks migration and causes the destination VM to no longer run after migration. We now encourage userspace to write the read and expected value of GICD_IIDR as the first part of a GIC register restore, and if we observe a write to GICD_IIDR we know that userspace has been updated and has had a chance to cope with older kernels (VGICv2 IIDR.Revision == 0) incorrectly reporting interrupts as group 1, and therefore we now allow groups to be user writable. Reviewed-by: Andrew Jones Signed-off-by: Christoffer Dall Signed-off-by: Marc Zyngier --- include/kvm/arm_vgic.h | 3 +++ virt/kvm/arm/vgic/vgic-mmio-v2.c | 16 +++++++++++++++- 2 files changed, 18 insertions(+), 1 deletion(-) diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h index c661d0ee6628..c134790be32c 100644 --- a/include/kvm/arm_vgic.h +++ b/include/kvm/arm_vgic.h @@ -221,6 +221,9 @@ struct vgic_dist { /* Implementation revision as reported in the GICD_IIDR */ u32 implementation_rev; + /* Userspace can write to GICv2 IGROUPR */ + bool v2_groups_user_writable; + /* Do injected MSIs require an additional device ID? */ bool msis_require_devid; diff --git a/virt/kvm/arm/vgic/vgic-mmio-v2.c b/virt/kvm/arm/vgic/vgic-mmio-v2.c index ee164f831401..26654f4140ed 100644 --- a/virt/kvm/arm/vgic/vgic-mmio-v2.c +++ b/virt/kvm/arm/vgic/vgic-mmio-v2.c @@ -85,6 +85,18 @@ static int vgic_mmio_uaccess_write_v2_misc(struct kvm_vcpu *vcpu, case GIC_DIST_IIDR: if (val != vgic_mmio_read_v2_misc(vcpu, addr, len)) return -EINVAL; + + /* + * If we observe a write to GICD_IIDR we know that userspace + * has been updated and has had a chance to cope with older + * kernels (VGICv2 IIDR.Revision == 0) incorrectly reporting + * interrupts as group 1, and therefore we now allow groups to + * be user writable. Doing this by default would break + * migration from old kernels to new kernels with legacy + * userspace. + */ + vcpu->kvm->arch.vgic.v2_groups_user_writable = true; + return 0; } vgic_mmio_write_v2_misc(vcpu, addr, len, val); @@ -95,7 +107,9 @@ static int vgic_mmio_uaccess_write_v2_group(struct kvm_vcpu *vcpu, gpa_t addr, unsigned int len, unsigned long val) { - /* Ignore writes from userspace */ + if (vcpu->kvm->arch.vgic.v2_groups_user_writable) + vgic_mmio_write_group(vcpu, addr, len, val); + return 0; }