From patchwork Thu Jan 23 13:47:48 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexandru Elisei X-Patchwork-Id: 11347933 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 48C23159A for ; Thu, 23 Jan 2020 13:48:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2798C24685 for ; Thu, 23 Jan 2020 13:48:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729095AbgAWNsh (ORCPT ); Thu, 23 Jan 2020 08:48:37 -0500 Received: from foss.arm.com ([217.140.110.172]:39750 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729096AbgAWNsg (ORCPT ); Thu, 23 Jan 2020 08:48:36 -0500 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 30D20106F; Thu, 23 Jan 2020 05:48:36 -0800 (PST) Received: from e123195-lin.cambridge.arm.com (e123195-lin.cambridge.arm.com [10.1.196.63]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 2BF943F68E; Thu, 23 Jan 2020 05:48:35 -0800 (PST) From: Alexandru Elisei To: kvm@vger.kernel.org Cc: will@kernel.org, julien.thierry.kdev@gmail.com, andre.przywara@arm.com, sami.mujawar@arm.com, lorenzo.pieralisi@arm.com, maz@kernel.org Subject: [PATCH v2 kvmtool 13/30] vfio/pci: Ignore expansion ROM BAR writes Date: Thu, 23 Jan 2020 13:47:48 +0000 Message-Id: <20200123134805.1993-14-alexandru.elisei@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200123134805.1993-1-alexandru.elisei@arm.com> References: <20200123134805.1993-1-alexandru.elisei@arm.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org To get the size of the expansion ROM, software writes 0xfffff800 to the expansion ROM BAR in the PCI configuration space. PCI emulation executes the optional configuration space write callback that a device can implement before emulating this write. VFIO doesn't have support for emulating expansion ROMs. However, the callback writes the guest value to the hardware BAR, and then it reads it back to the BAR to make sure the write has completed successfully. After this, we return to regular PCI emulation and because the BAR is no longer 0, we write back to the BAR the value that the guest used to get the size. As a result, the guest will think that the ROM size is 0x800 after the subsequent read and we end up unintentionally exposing to the guest a BAR which we don't emulate. Let's fix this by ignoring writes to the expansion ROM BAR. Signed-off-by: Alexandru Elisei --- vfio/pci.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/vfio/pci.c b/vfio/pci.c index 1bdc20038411..1f38f90c3ae9 100644 --- a/vfio/pci.c +++ b/vfio/pci.c @@ -472,6 +472,9 @@ static void vfio_pci_cfg_write(struct kvm *kvm, struct pci_device_header *pci_hd struct vfio_device *vdev; void *base = pci_hdr; + if (offset == PCI_ROM_ADDRESS) + return; + pdev = container_of(pci_hdr, struct vfio_pci_device, hdr); vdev = container_of(pdev, struct vfio_device, pci); info = &vdev->regions[VFIO_PCI_CONFIG_REGION_INDEX].info;