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Message-ID: <388e7af7-be76-61a3-a9ce-9a148097610e@linux.ibm.com>
Date: Mon, 22 Aug 2022 10:36:03 +0200
From: Pierre Morel <pmorel@...ux.ibm.com>
To: Randy Dunlap <rdunlap@...radead.org>, mjrosato@...ux.ibm.com
Cc: linux-kernel@...r.kernel.org, lkp@...el.com,
borntraeger@...ux.ibm.com, farman@...ux.ibm.com,
linux-s390@...r.kernel.org, kvm@...r.kernel.org, gor@...ux.ibm.com,
hca@...ux.ibm.com, schnelle@...ux.ibm.com, frankja@...ux.ibm.com,
alex.williamson@...hat.com, cohuck@...hat.com
Subject: Re: [PATCH v2] KVM: s390: pci: Hook to access KVM lowlevel from VFIO
On 8/19/22 23:10, Randy Dunlap wrote:
>
>
> On 8/19/22 05:29, Pierre Morel wrote:
>> We have a cross dependency between KVM and VFIO 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.
>>
>> Reported-by: Randy Dunlap <rdunlap@...radead.org>
>> Reported-by: kernel test robot <lkp@...el.com>
>> Reviewed-by: Matthew Rosato <mjrosato@...ux.ibm.com>
>> Reviewed-by: Niklas Schnelle <schnelle@...ux.ibm.com>
>> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
>> Fixes: 09340b2fca007 ("KVM: s390: pci: add routines to start/stop interpretive execution")
>> Cc: <stable@...r.kernel.org>
>
> Acked-by: Randy Dunlap <rdunlap@...radead.org> # build-tested
>
> Thanks.
Thanks Randy,
Regards,
Pierre
>
>> ---
>> arch/s390/include/asm/kvm_host.h | 17 ++++++-----------
>> arch/s390/kvm/pci.c | 12 ++++++++----
>> arch/s390/pci/Makefile | 2 +-
>> arch/s390/pci/pci_kvm_hook.c | 11 +++++++++++
>> drivers/vfio/pci/vfio_pci_zdev.c | 8 ++++++--
>> 5 files changed, 32 insertions(+), 18 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..b1e98a9ed152 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 zpci_kvm_hook {
>> + int (*kvm_register)(void *opaque, struct kvm *kvm);
>> + void (*kvm_unregister)(void *opaque);
>> +};
>> +
>> +extern struct zpci_kvm_hook zpci_kvm_hook;
>>
>> #endif
>> diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
>> index 4946fb7757d6..bb8c335d17b9 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);
>> + zpci_kvm_hook.kvm_register = kvm_s390_pci_register_kvm;
>> + zpci_kvm_hook.kvm_unregister = kvm_s390_pci_unregister_kvm;
>>
>> return 0;
>> }
>> @@ -685,6 +687,8 @@ int kvm_s390_pci_init(void)
>> void kvm_s390_pci_exit(void)
>> {
>> mutex_destroy(&aift->aift_lock);
>> + zpci_kvm_hook.kvm_register = NULL;
>> + zpci_kvm_hook.kvm_unregister = NULL;
>>
>> kfree(aift);
>> }
>> diff --git a/arch/s390/pci/Makefile b/arch/s390/pci/Makefile
>> index bf557a1b789c..5ae31ca9dd44 100644
>> --- a/arch/s390/pci/Makefile
>> +++ b/arch/s390/pci/Makefile
>> @@ -5,5 +5,5 @@
>>
>> obj-$(CONFIG_PCI) += pci.o pci_irq.o pci_dma.o pci_clp.o pci_sysfs.o \
>> pci_event.o pci_debug.o pci_insn.o pci_mmio.o \
>> - pci_bus.o
>> + pci_bus.o pci_kvm_hook.o
>> obj-$(CONFIG_PCI_IOV) += pci_iov.o
>> diff --git a/arch/s390/pci/pci_kvm_hook.c b/arch/s390/pci/pci_kvm_hook.c
>> new file mode 100644
>> index 000000000000..ff34baf50a3e
>> --- /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@...ux.ibm.com>
>> + */
>> +#include <linux/kvm_host.h>
>> +
>> +struct zpci_kvm_hook zpci_kvm_hook;
>> +EXPORT_SYMBOL_GPL(zpci_kvm_hook);
>> diff --git a/drivers/vfio/pci/vfio_pci_zdev.c b/drivers/vfio/pci/vfio_pci_zdev.c
>> index e163aa9f6144..0cbdcd14f1c8 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 (zpci_kvm_hook.kvm_register)
>> + return zpci_kvm_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 (zpci_kvm_hook.kvm_unregister)
>> + zpci_kvm_hook.kvm_unregister(zdev);
>> }
>
--
Pierre Morel
IBM Lab Boeblingen
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