Re: [PATCH] KVM: s390: pci: VFIO_PCI ZDEV configuration fix

Matthew Rosato
2022-08-16T22:15:50Z

On 8/16/22 4:28 PM, Pierre Morel wrote:
> Fixing configuration for VFIO PCI interpretation.
>
> 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..")
> Fixes: c435c54639aa5 ("vfio/pci: introduce CONFIG_VFIO_PCI_ZDEV_KVM..")
> Cc: <stable@vger.kernel.org>
> ---
> arch/s390/include/asm/kvm_host.h | 9 ---------
> arch/s390/kvm/Makefile | 2 +-
> arch/s390/kvm/pci.c | 4 ++--
> drivers/vfio/pci/Kconfig | 4 ++--
> include/linux/vfio_pci_core.h | 2 +-
> 5 files changed, 6 insertions(+), 15 deletions(-)
>
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index f39092e0ceaa..f6cf961731af 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -1038,16 +1038,7 @@ 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
>
> #endif
> diff --git a/arch/s390/kvm/Makefile b/arch/s390/kvm/Makefile
> index 02217fb4ae10..be36afcfd6ff 100644
> --- a/arch/s390/kvm/Makefile
> +++ b/arch/s390/kvm/Makefile
> @@ -9,6 +9,6 @@ ccflags-y := -Ivirt/kvm -Iarch/s390/kvm
>
> kvm-y += kvm-s390.o intercept.o interrupt.o priv.o sigp.o
> kvm-y += diag.o gaccess.o guestdbg.o vsie.o pv.o
> +kvm-y += pci.o
>
> -kvm-$(CONFIG_VFIO_PCI_ZDEV_KVM) += pci.o

You would need to switch this to CONFIG_PCI at least, else we get build errors with CONFIG_PCI=n.

> obj-$(CONFIG_KVM) += kvm.o
> diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
> index 4946fb7757d6..cf8ab72a2109 100644
> --- a/arch/s390/kvm/pci.c
> +++ b/arch/s390/kvm/pci.c
> @@ -435,7 +435,7 @@ int kvm_s390_pci_register_kvm(struct zpci_dev *zdev, struct kvm *kvm)
> {
> int rc;
>
> - if (!zdev)
> + if (!IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM) || !zdev)
> return -EINVAL;
>
> mutex_lock(&zdev->kzdev_lock);
> @@ -516,7 +516,7 @@ void kvm_s390_pci_unregister_kvm(struct zpci_dev *zdev)
> {
> struct kvm *kvm;
>
> - if (!zdev)
> + if (!IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM) || !zdev)
> return;
>
> mutex_lock(&zdev->kzdev_lock);
> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
> index f9d0c908e738..bbc375b028ef 100644
> --- a/drivers/vfio/pci/Kconfig
> +++ b/drivers/vfio/pci/Kconfig
> @@ -45,9 +45,9 @@ config VFIO_PCI_IGD
> endif
>
> config VFIO_PCI_ZDEV_KVM
> - bool "VFIO PCI extensions for s390x KVM passthrough"
> + def_tristate y
> + prompt "VFIO PCI extensions for s390x KVM passthrough"
> depends on S390 && KVM
> - default y
> help
> Support s390x-specific extensions to enable support for enhancements
> to KVM passthrough capabilities, such as interpretive execution of
> diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
> index 5579ece4347b..7db3bb8129b1 100644
> --- a/include/linux/vfio_pci_core.h
> +++ b/include/linux/vfio_pci_core.h
> @@ -205,7 +205,7 @@ static inline int vfio_pci_igd_init(struct vfio_pci_core_device *vdev)
> }
> #endif
>
> -#ifdef CONFIG_VFIO_PCI_ZDEV_KVM
> +#if IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM)
> int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
> struct vfio_info_cap *caps);
> int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev);

This still doesn't seem quite right... I tried some variations:

1)
CONFIG_KVM=m
CONFIG_VFIO_PCI_CORE=m
CONFIG_VFIO_PCI=m
CONFIG_VFIO_PCI_ZDEV_KVM=m

compiles, works with a small change:

diff --git a/include/linux/sched/user.h b/include/linux/sched/user.h
index f054d0360a75..99734e135420 100644
--- a/include/linux/sched/user.h
+++ b/include/linux/sched/user.h
@@ -25,7 +25,7 @@ struct user_struct {

#if defined(CONFIG_PERF_EVENTS) || defined(CONFIG_BPF_SYSCALL) || \
defined(CONFIG_NET) || defined(CONFIG_IO_URING) || \
- defined(CONFIG_VFIO_PCI_ZDEV_KVM)
+ IS_ENABLED(CONFIG_VFIO_PCI_ZDEV_KVM)

2)
CONFIG_KVM=y
CONFIG_VFIO_PCI_CORE=m
CONFIG_VFIO_PCI=m
CONFIG_VFIO_PCI_ZDEV_KVM=m

compiles, works with above user.h change

3)
CONFIG_KVM=y
CONFIG_VFIO_PCI_CORE=y
CONFIG_VFIO_PCI=y
CONFIG_VFIO_PCI_ZDEV_KVM=y

compiles, works with above user.h change

4)
CONFIG_KVM=m
CONFIG_VFIO_PCI_CORE=y
CONFIG_VFIO_PCI=y
CONFIG_VFIO_PCI_ZDEV_KVM=m

fails with:

ld: drivers/vfio/pci/vfio_pci_core.o: in function `vfio_pci_core_enable':
/usr/src/linux/drivers/vfio/pci/vfio_pci_core.c:320: undefined reference to `vfio_pci_zdev_open_device'
ld: /usr/src/linux/drivers/vfio/pci/vfio_pci_core.c:349: undefined reference to `vfio_pci_zdev_close_device'
ld: drivers/vfio/pci/vfio_pci_core.o: in function `vfio_pci_core_disable':
/usr/src/linux/drivers/vfio/pci/vfio_pci_core.c:428: undefined reference to `vfio_pci_zdev_close_device'
ld: drivers/vfio/pci/vfio_pci_core.o: in function `vfio_pci_core_ioctl':
/usr/src/linux/drivers/vfio/pci/vfio_pci_core.c:712: undefined reference to `vfio_pci_info_zdev_add_caps'

5)
CONFIG_KVM=m
CONFIG_VFIO_PCI_CORE=y
CONFIG_VFIO_PCI=y
CONFIG_VFIO_PCI_ZDEV_KVM=y

This forces CONFIG_VFIO_PCI_ZDEV_KVM to 'm' and fails as above.