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Thu, 18 Aug 2022 13:33:34 +0000 (GMT) Message-ID: Date: Thu, 18 Aug 2022 09:33:33 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH] KVM: s390: pci: Hook to access KVM lowlevel from VFIO Content-Language: en-US To: Pierre Morel Cc: rdunlap@infradead.org, linux-kernel@vger.kernel.org, lkp@intel.com, borntraeger@linux.ibm.com, farman@linux.ibm.com, linux-s390@vger.kernel.org, kvm@vger.kernel.org, gor@linux.ibm.com, hca@linux.ibm.com, schnelle@linux.ibm.com References: <1f2dd65e-b79b-44df-cc6a-8b3aa8fd61af@linux.ibm.com> <20220818102305.250702-1-pmorel@linux.ibm.com> From: Matthew Rosato In-Reply-To: <20220818102305.250702-1-pmorel@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: FigZBCJFWbFgQBLROQY8dciMYS1QdHAO X-Proofpoint-GUID: FigZBCJFWbFgQBLROQY8dciMYS1QdHAO X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-08-18_12,2022-08-18_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=999 priorityscore=1501 lowpriorityscore=0 spamscore=0 clxscore=1015 phishscore=0 impostorscore=0 adultscore=0 suspectscore=0 mlxscore=0 bulkscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2207270000 definitions=main-2208180047 X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/18/22 6:23 AM, Pierre Morel wrote: > We have a cross dependency between KVM and VFIO. maybe add something like 'when using s390 vfio_pci_zdev extensions for PCI passthrough' > To be able to keep both subsystem modular we add a registering > hook inside the S390 core code. > > This fixes a build problem when VFIO is built-in and KVM is built > as a module or excluded. s/or excluded// There's no problem when KVM is excluded, that forces CONFIG_VFIO_PCI_ZDEV_KVM=n because of the 'depends on S390 && KVM'. > > Reported-by: Randy Dunlap > Reported-by: kernel test robot > Signed-off-by: Pierre Morel > Fixes: 09340b2fca007 ("KVM: s390: pci: add routines to start/stop inter..") > Cc: > --- > arch/s390/include/asm/kvm_host.h | 17 ++++++----------- > arch/s390/kvm/pci.c | 10 ++++++---- > arch/s390/pci/Makefile | 2 ++ > arch/s390/pci/pci_kvm_hook.c | 11 +++++++++++ > drivers/vfio/pci/vfio_pci_zdev.c | 8 ++++++-- > 5 files changed, 31 insertions(+), 17 deletions(-) > create mode 100644 arch/s390/pci/pci_kvm_hook.c > > diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h > index f39092e0ceaa..8312ed9d1937 100644 > --- a/arch/s390/include/asm/kvm_host.h > +++ b/arch/s390/include/asm/kvm_host.h > @@ -1038,16 +1038,11 @@ static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) {} > #define __KVM_HAVE_ARCH_VM_FREE > void kvm_arch_free_vm(struct kvm *kvm); > > -#ifdef CONFIG_VFIO_PCI_ZDEV_KVM > -int kvm_s390_pci_register_kvm(struct zpci_dev *zdev, struct kvm *kvm); > -void kvm_s390_pci_unregister_kvm(struct zpci_dev *zdev); > -#else > -static inline int kvm_s390_pci_register_kvm(struct zpci_dev *dev, > - struct kvm *kvm) > -{ > - return -EPERM; > -} > -static inline void kvm_s390_pci_unregister_kvm(struct zpci_dev *dev) {} > -#endif > +struct kvm_register_hook { Nit: zpci_kvm_register_hook ? Just to make it clear it's for zpci. > + int (*kvm_register)(void *opaque, struct kvm *kvm); > + void (*kvm_unregister)(void *opaque); > +}; > + > +extern struct kvm_register_hook kvm_pci_hook; Nit: kvm_zpci_hook ? > > #endif > diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c > index 4946fb7757d6..e173fce64c4f 100644 > --- a/arch/s390/kvm/pci.c > +++ b/arch/s390/kvm/pci.c > @@ -431,8 +431,9 @@ static void kvm_s390_pci_dev_release(struct zpci_dev *zdev) > * available, enable them and let userspace indicate whether or not they will > * be used (specify SHM bit to disable). > */ > -int kvm_s390_pci_register_kvm(struct zpci_dev *zdev, struct kvm *kvm) > +static int kvm_s390_pci_register_kvm(void *opaque, struct kvm *kvm) > { > + struct zpci_dev *zdev = opaque; > int rc; > > if (!zdev) > @@ -510,10 +511,10 @@ int kvm_s390_pci_register_kvm(struct zpci_dev *zdev, struct kvm *kvm) > kvm_put_kvm(kvm); > return rc; > } > -EXPORT_SYMBOL_GPL(kvm_s390_pci_register_kvm); > > -void kvm_s390_pci_unregister_kvm(struct zpci_dev *zdev) > +static void kvm_s390_pci_unregister_kvm(void *opaque) > { > + struct zpci_dev *zdev = opaque; > struct kvm *kvm; > > if (!zdev) > @@ -566,7 +567,6 @@ void kvm_s390_pci_unregister_kvm(struct zpci_dev *zdev) > > kvm_put_kvm(kvm); > } > -EXPORT_SYMBOL_GPL(kvm_s390_pci_unregister_kvm); > > void kvm_s390_pci_init_list(struct kvm *kvm) > { > @@ -678,6 +678,8 @@ int kvm_s390_pci_init(void) > > spin_lock_init(&aift->gait_lock); > mutex_init(&aift->aift_lock); > + kvm_pci_hook.kvm_register = kvm_s390_pci_register_kvm; > + kvm_pci_hook.kvm_unregister = kvm_s390_pci_unregister_kvm; > > return 0; > } > diff --git a/arch/s390/pci/Makefile b/arch/s390/pci/Makefile > index bf557a1b789c..c02dbfb415d9 100644 > --- a/arch/s390/pci/Makefile > +++ b/arch/s390/pci/Makefile > @@ -7,3 +7,5 @@ obj-$(CONFIG_PCI) += pci.o pci_irq.o pci_dma.o pci_clp.o pci_sysfs.o \ > pci_event.o pci_debug.o pci_insn.o pci_mmio.o \ > pci_bus.o > obj-$(CONFIG_PCI_IOV) += pci_iov.o > + > +obj-y += pci_kvm_hook.o I guess it doesn't harm anything to add this unconditionally, but I think it would also be OK to just include this in the CONFIG_PCI list - vfio_pci_zdev and arch/s390/kvm/pci all rely on CONFIG_PCI via CONFIG_VFIO_PCI_ZDEV_KVM which implies PCI via VFIO_PCI. > diff --git a/arch/s390/pci/pci_kvm_hook.c b/arch/s390/pci/pci_kvm_hook.c > new file mode 100644 > index 000000000000..9d8799b72dbf > --- /dev/null > +++ b/arch/s390/pci/pci_kvm_hook.c > @@ -0,0 +1,11 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * VFIO ZPCI devices support > + * > + * Copyright (C) IBM Corp. 2022. All rights reserved. > + * Author(s): Pierre Morel > + */ > +#include > + > +struct kvm_register_hook kvm_pci_hook; > +EXPORT_SYMBOL_GPL(kvm_pci_hook); Following the comments above, zpci_kvm_register_hook, kvm_zpci_hook ? I'm not sure if this really needs to be in a separate file or if it could just go into arch/s390/pci.c with the zpci_aipb -- If going the route of a separate file, up to Niklas whether he wants this under the S390 PCI maintainership or added to the list for s390 vfio-pci like arch/kvm/pci* and vfio_pci_zdev. > diff --git a/drivers/vfio/pci/vfio_pci_zdev.c b/drivers/vfio/pci/vfio_pci_zdev.c > index e163aa9f6144..3b7a707e2fe5 100644 > --- a/drivers/vfio/pci/vfio_pci_zdev.c > +++ b/drivers/vfio/pci/vfio_pci_zdev.c > @@ -151,7 +151,10 @@ int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev) > if (!vdev->vdev.kvm) > return 0; > > - return kvm_s390_pci_register_kvm(zdev, vdev->vdev.kvm); > + if (kvm_pci_hook.kvm_register) > + return kvm_pci_hook.kvm_register(zdev, vdev->vdev.kvm); > + > + return -ENOENT; > } > > void vfio_pci_zdev_close_device(struct vfio_pci_core_device *vdev) > @@ -161,5 +164,6 @@ void vfio_pci_zdev_close_device(struct vfio_pci_core_device *vdev) > if (!zdev || !vdev->vdev.kvm) > return; > > - kvm_s390_pci_unregister_kvm(zdev); > + if (kvm_pci_hook.kvm_unregister) > + return kvm_pci_hook.kvm_unregister(zdev); No need for the return here, this is a void function calling a void function. Overall, this looks good to me and survives a series of compile and device passthrough tests on my end, just a matter of a few of these minor comments above. Thanks for tackling this Pierre!