From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:58106 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726512AbgHLSEL (ORCPT ); Wed, 12 Aug 2020 14:04:11 -0400 Subject: Re: [PATCH] PCI: Introduce flag for detached virtual functions References: <1597243817-3468-1-git-send-email-mjrosato@linux.ibm.com> <1597243817-3468-2-git-send-email-mjrosato@linux.ibm.com> <20200812104351.3668cc0f@x1.home> From: Matthew Rosato Message-ID: <05c46459-7d00-c01c-6387-68bc7d6c4f63@linux.ibm.com> Date: Wed, 12 Aug 2020 14:04:01 -0400 MIME-Version: 1.0 In-Reply-To: <20200812104351.3668cc0f@x1.home> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Alex Williamson Cc: bhelgaas@google.com, schnelle@linux.ibm.com, pmorel@linux.ibm.com, mpe@ellerman.id.au, oohall@gmail.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-pci@vger.kernel.org On 8/12/20 12:43 PM, Alex Williamson wrote: > On Wed, 12 Aug 2020 10:50:17 -0400 > Matthew Rosato wrote: > >> s390x has the notion of providing VFs to the kernel in a manner >> where the associated PF is inaccessible other than via firmware. >> These are not treated as typical VFs and access to them is emulated >> by underlying firmware which can still access the PF. After >> abafbc55 however these detached VFs were no longer able to work >> with vfio-pci as the firmware does not provide emulation of the >> PCI_COMMAND_MEMORY bit. In this case, let's explicitly recognize >> these detached VFs so that vfio-pci can allow memory access to >> them again. >> >> Signed-off-by: Matthew Rosato >> Reviewed-by: Pierre Morel >> Reviewed-by: Niklas Schnelle >> --- >> arch/s390/pci/pci.c | 8 ++++++++ >> drivers/vfio/pci/vfio_pci_config.c | 3 ++- >> include/linux/pci.h | 1 + >> 3 files changed, 11 insertions(+), 1 deletion(-) >> >> diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c >> index 3902c9f..04ac76d 100644 >> --- a/arch/s390/pci/pci.c >> +++ b/arch/s390/pci/pci.c >> @@ -581,6 +581,14 @@ int pcibios_enable_device(struct pci_dev *pdev, int mask) >> { >> struct zpci_dev *zdev = to_zpci(pdev); >> >> + /* >> + * If we have a VF on a non-multifunction bus, it must be a VF that is >> + * detached from its parent PF. We rely on firmware emulation to >> + * provide underlying PF details. >> + */ >> + if (zdev->vfn && !zdev->zbus->multifunction) >> + pdev->detached_vf = 1; >> + >> zpci_debug_init_device(zdev, dev_name(&pdev->dev)); >> zpci_fmb_enable_device(zdev); >> >> diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c >> index d98843f..17845fc 100644 >> --- a/drivers/vfio/pci/vfio_pci_config.c >> +++ b/drivers/vfio/pci/vfio_pci_config.c >> @@ -406,7 +406,8 @@ bool __vfio_pci_memory_enabled(struct vfio_pci_device *vdev) >> * PF SR-IOV capability, there's therefore no need to trigger >> * faults based on the virtual value. >> */ >> - return pdev->is_virtfn || (cmd & PCI_COMMAND_MEMORY); >> + return pdev->is_virtfn || pdev->detached_vf || >> + (cmd & PCI_COMMAND_MEMORY); >> } >> >> /* > > Wouldn't we also want to enable the is_virtfn related code in > vfio_basic_config_read() and at least the initial setting of the > command register in vfio_config_init()? Otherwise we're extending the > incomplete emulation out to userspace. Thanks, > We had discussed doing this internally and I ultimately left it out of this patch to keep the changes small... But I agree that it makes sense to fix the emulation for userspace. I can add the changes you suggest + would also need to change vfio_restore_bar() with: - if (pdev->is_virtfn) + if (pdev->is_virtfn || pdev->detached_vf) return; to prevent the config changes from tripping the restore code. I'll send a V2 with this included.