Messages in this thread | | | Date | Thu, 18 Aug 2022 16:06:04 +0200 | Subject | Re: [PATCH] KVM: s390: pci: Hook to access KVM lowlevel from VFIO | From | Pierre Morel <> |
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On 8/18/22 15:33, Matthew Rosato wrote: > 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'.
OK
> >> >> Reported-by: Randy Dunlap <rdunlap@infradead.org> >> Reported-by: kernel test robot <lkp@intel.com> >> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com> >> Fixes: 09340b2fca007 ("KVM: s390: pci: add routines to start/stop inter..") >> Cc: <stable@vger.kernel.org> >> --- >> 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.
OK
> >> + 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 ?
OK too,
> >> >> #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.
Right,CONFIG_PCI is a bool so we can put the hook in arch/s390/pci/pci.c and use a defined(CONFIG_PCI) to protect the initialization inside KVM.
> >> 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 <pmorel@linux.ibm.com> >> + */ >> +#include <linux/kvm_host.h> >> + >> +struct kvm_register_hook kvm_pci_hook; >> +EXPORT_SYMBOL_GPL(kvm_pci_hook); > > Following the comments above, zpci_kvm_register_hook, kvm_zpci_hook ?
OK
> > 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.
agreed no need for a separate file, it is much better.
> >> 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.
right.
> > > 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! >
Thanks, Pierre
-- Pierre Morel IBM Lab Boeblingen
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