From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:3742 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391692AbhASUvZ (ORCPT ); Tue, 19 Jan 2021 15:51:25 -0500 Subject: Re: [PATCH 0/4] vfio-pci/zdev: Fixing s390 vfio-pci ISM support From: Matthew Rosato References: <1611086550-32765-1-git-send-email-mjrosato@linux.ibm.com> Message-ID: <8b655baa-cda0-a78f-4504-649e9580c87a@linux.ibm.com> Date: Tue, 19 Jan 2021 15:50:35 -0500 MIME-Version: 1.0 In-Reply-To: <1611086550-32765-1-git-send-email-mjrosato@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit List-ID: To: alex.williamson@redhat.com, cohuck@redhat.com, schnelle@linux.ibm.com Cc: pmorel@linux.ibm.com, borntraeger@de.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, gerald.schaefer@linux.ibm.com, linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org On 1/19/21 3:02 PM, Matthew Rosato wrote: > Today, ISM devices are completely disallowed for vfio-pci passthrough as > QEMU will reject the device due to an (inappropriate) MSI-X check. > However, in an effort to enable ISM device passthrough, I realized that the > manner in which ISM performs block write operations is highly incompatible > with the way that QEMU s390 PCI instruction interception and > vfio_pci_bar_rw break up I/O operations into 8B and 4B operations -- ISM > devices have particular requirements in regards to the alignment, size and > order of writes performed. Furthermore, they require that legacy/non-MIO > s390 PCI instructions are used, which is also not guaranteed when the I/O > is passed through the typical userspace channels. > > As a result, this patchset proposes a new VFIO region to allow a guest to > pass certain PCI instruction intercepts directly to the s390 host kernel > PCI layer for execution, pinning the guest buffer in memory briefly in > order to execute the requested PCI instruction. > > Changes from RFC -> v1: > - No functional changes, just minor commentary changes -- Re-posting along > with updated QEMU set. > Link to latest QEMU patch set: https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg04881.html > Matthew Rosato (4): > s390/pci: track alignment/length strictness for zpci_dev > vfio-pci/zdev: Pass the relaxed alignment flag > s390/pci: Get hardware-reported max store block length > vfio-pci/zdev: Introduce the zPCI I/O vfio region > > arch/s390/include/asm/pci.h | 4 +- > arch/s390/include/asm/pci_clp.h | 7 +- > arch/s390/pci/pci_clp.c | 2 + > drivers/vfio/pci/vfio_pci.c | 8 ++ > drivers/vfio/pci/vfio_pci_private.h | 6 ++ > drivers/vfio/pci/vfio_pci_zdev.c | 160 ++++++++++++++++++++++++++++++++++++ > include/uapi/linux/vfio.h | 4 + > include/uapi/linux/vfio_zdev.h | 34 ++++++++ > 8 files changed, 222 insertions(+), 3 deletions(-) >