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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 61EAEC43381 for ; Thu, 14 Feb 2019 18:27:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 367C621B68 for ; Thu, 14 Feb 2019 18:27:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393319AbfBNS1W (ORCPT ); Thu, 14 Feb 2019 13:27:22 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42706 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727954AbfBNS1W (ORCPT ); Thu, 14 Feb 2019 13:27:22 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7466558580; Thu, 14 Feb 2019 18:27:21 +0000 (UTC) Received: from [10.36.116.102] (ovpn-116-102.ams2.redhat.com [10.36.116.102]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5E1E717D38; Thu, 14 Feb 2019 18:27:17 +0000 (UTC) Subject: Re: [PATCH v2] vfio_pci: Enable memory accesses before calling pci_map_rom To: Alex Williamson Cc: eric.auger.pro@gmail.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <20190213110610.4834-1-eric.auger@redhat.com> <20190213105200.1deafb62@w520.home> From: Auger Eric Message-ID: <015103e3-c317-22f3-e209-f5ccf890bafb@redhat.com> Date: Thu, 14 Feb 2019 19:27:15 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190213105200.1deafb62@w520.home> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 14 Feb 2019 18:27:21 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Alex, On 2/13/19 6:52 PM, Alex Williamson wrote: > On Wed, 13 Feb 2019 12:06:10 +0100 > Eric Auger wrote: > >> pci_map_rom/pci_get_rom_size() performs memory access in the ROM. >> In case the Memory Space accesses were disabled, readw() is likely to >> crash the host with a synchronous external abort (aarch64). > > As implied in response to Konrad, the likeliness really depends on the > whole platform, not just the CPU architecture. It's a class of > problems that depends on OS control or error handling, which we simply > don't have on many systems. But we can fix this instance of it. Agreed, I just hit this issue on one specific aarch64 machine > >> In case memory accesses were disabled, re-enable them before the call >> and disable them back again just after. >> >> Signed-off-by: Eric Auger > > This has been around since the beginning, but maybe a Fixes tag would > be useful: > > Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver") OK > >> >> --- >> >> v1 -> v2: >> - also re-enable in case of error >> --- >> drivers/vfio/pci/vfio_pci.c | 17 ++++++++++++++++- >> 1 file changed, 16 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c >> index ff60bd1ea587..721aa55424a4 100644 >> --- a/drivers/vfio/pci/vfio_pci.c >> +++ b/drivers/vfio/pci/vfio_pci.c >> @@ -706,8 +706,10 @@ static long vfio_pci_ioctl(void *device_data, >> break; >> case VFIO_PCI_ROM_REGION_INDEX: >> { >> + bool mem_access_disabled; >> void __iomem *io; >> size_t size; >> + u16 cmd; >> >> info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index); >> info.flags = 0; >> @@ -723,15 +725,28 @@ static long vfio_pci_ioctl(void *device_data, >> break; >> } >> >> + pci_read_config_word(pdev, PCI_COMMAND, &cmd); >> + mem_access_disabled = !(cmd & PCI_COMMAND_MEMORY); >> + if (mem_access_disabled) { >> + cmd |= PCI_COMMAND_MEMORY; >> + pci_write_config_word(pdev, PCI_COMMAND, cmd); >> + } >> + >> /* Is it really there? */ >> io = pci_map_rom(pdev, &size); >> if (!io || !size) { >> info.size = 0; >> - break; >> + goto rom_info_out; >> } >> pci_unmap_rom(pdev, io); >> >> info.flags = VFIO_REGION_INFO_FLAG_READ; >> +rom_info_out: >> + if (mem_access_disabled) { >> + cmd &= ~PCI_COMMAND_MEMORY; >> + pci_write_config_word(pdev, PCI_COMMAND, cmd); >> + } >> + >> break; >> } >> case VFIO_PCI_VGA_REGION_INDEX: > > I don't think we need to be so timid about the command register and we > can also avoid the goto by modifying the test (testing io and size in > the original is probably overly paranoid), perhaps simply: Yes looks fine. Do you want to respin or do you prefer I do? Thanks Eric > > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c > index ff60bd1ea587..659b7c1ea8fb 100644 > --- a/drivers/vfio/pci/vfio_pci.c > +++ b/drivers/vfio/pci/vfio_pci.c > @@ -708,6 +708,7 @@ static long vfio_pci_ioctl(void *device_data, > { > void __iomem *io; > size_t size; > + u16 orig_cmd; > > info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index); > info.flags = 0; > @@ -723,15 +724,23 @@ static long vfio_pci_ioctl(void *device_data, > break; > } > > - /* Is it really there? */ > + /* > + * Is it really there? Enable memory decode for > + * implicit access in pci_map_rom(). > + */ > + pci_read_config_word(pdev, PCI_COMMAND, &orig_cmd); > + pci_write_config_word(pdev, PCI_COMMAND, > + orig_cmd | PCI_COMMAND_MEMORY); > + > io = pci_map_rom(pdev, &size); > - if (!io || !size) { > + if (io) { > + info.flags = VFIO_REGION_INFO_FLAG_READ; > + pci_unmap_rom(pdev, io); > + } else > info.size = 0; > - break; > - } > - pci_unmap_rom(pdev, io); > > - info.flags = VFIO_REGION_INFO_FLAG_READ; > + pci_write_config_word(pdev, PCI_COMMAND, orig_cmd); > + > break; > } > case VFIO_PCI_VGA_REGION_INDEX: >