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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 3A14DCA9EC2 for ; Tue, 29 Oct 2019 07:21:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 18BCB2067D for ; Tue, 29 Oct 2019 07:21:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730244AbfJ2HVK (ORCPT ); Tue, 29 Oct 2019 03:21:10 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:40378 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728111AbfJ2HU2 (ORCPT ); Tue, 29 Oct 2019 03:20:28 -0400 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 453D89AEB92ADC6E058B; Tue, 29 Oct 2019 15:20:27 +0800 (CST) Received: from DESKTOP-8RFUVS3.china.huawei.com (10.173.222.27) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.439.0; Tue, 29 Oct 2019 15:20:17 +0800 From: Zenghui Yu To: , , , , CC: , , , , Zenghui Yu Subject: [PATCH 3/3] KVM: arm/arm64: vgic: Don't rely on the wrong pending table Date: Tue, 29 Oct 2019 15:19:19 +0800 Message-ID: <20191029071919.177-4-yuzenghui@huawei.com> X-Mailer: git-send-email 2.23.0.windows.1 In-Reply-To: <20191029071919.177-1-yuzenghui@huawei.com> References: <20191029071919.177-1-yuzenghui@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.173.222.27] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It's possible that two LPIs locate in the same "byte_offset" but target two different vcpus, where their pending status are indicated by two different pending tables. In such a scenario, using last_byte_offset optimization will lead KVM relying on the wrong pending table entry. Let us use last_ptr instead, which can be treated as a byte index into a pending table and also, can be vcpu specific. Signed-off-by: Zenghui Yu --- If this patch has done the right thing, we can even add the: Fixes: 280771252c1b ("KVM: arm64: vgic-v3: KVM_DEV_ARM_VGIC_SAVE_PENDING_TABLES") But to be honest, I'm not clear about what has this patch actually fixed. Pending tables should contain all zeros before we flush vgic_irq's pending status into guest's RAM (thinking that guest should never write anything into it). So the pending table entry we've read from the guest memory seems always be zero. And we will always do the right thing even if we rely on the wrong pending table entry. I think I must have some misunderstanding here... Please fix me. virt/kvm/arm/vgic/vgic-v3.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c index 5ef93e5041e1..7cd2e2f81513 100644 --- a/virt/kvm/arm/vgic/vgic-v3.c +++ b/virt/kvm/arm/vgic/vgic-v3.c @@ -363,8 +363,8 @@ int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq) int vgic_v3_save_pending_tables(struct kvm *kvm) { struct vgic_dist *dist = &kvm->arch.vgic; - int last_byte_offset = -1; struct vgic_irq *irq; + gpa_t last_ptr = -1; int ret; u8 val; @@ -384,11 +384,11 @@ int vgic_v3_save_pending_tables(struct kvm *kvm) bit_nr = irq->intid % BITS_PER_BYTE; ptr = pendbase + byte_offset; - if (byte_offset != last_byte_offset) { + if (ptr != last_ptr) { ret = kvm_read_guest_lock(kvm, ptr, &val, 1); if (ret) return ret; - last_byte_offset = byte_offset; + last_ptr = ptr; } stored = val & (1U << bit_nr); -- 2.19.1