Re: [PATCH 04/26] vfio: Add struct to hold KVM assets and dedup group vs. iommufd code

Alex Williamson
2023-09-28T22:22:19Z

On Fri, 15 Sep 2023 17:30:56 -0700
Sean Christopherson <seanjc@google.com> wrote:

> Add a struct to hold the KVM assets need to manage and pass along KVM
> references to VFIO devices. Providing a common struct deduplicates the
> group vs. iommufd code, and will make it easier to rework the attachment
> logic so that VFIO doesn't have to do a symbol lookup to retrieve the
> get/put helpers from KVM.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> drivers/vfio/device_cdev.c | 9 +-------
> drivers/vfio/group.c | 18 ++--------------
> drivers/vfio/vfio.h | 22 +++++++++----------
> drivers/vfio/vfio_main.c | 43 +++++++++++++++++++++++++++-----------
> 4 files changed, 45 insertions(+), 47 deletions(-)

Reviewed-by: Alex Williamson <alex.williamson@redhat.com>

> diff --git a/drivers/vfio/device_cdev.c b/drivers/vfio/device_cdev.c
> index e75da0a70d1f..e484d6d6400a 100644
> --- a/drivers/vfio/device_cdev.c
> +++ b/drivers/vfio/device_cdev.c
> @@ -46,13 +46,6 @@ int vfio_device_fops_cdev_open(struct inode *inode, struct file *filep)
> return ret;
> }
>
> -static void vfio_df_get_kvm_safe(struct vfio_device_file *df)
> -{
> - spin_lock(&df->kvm_ref_lock);
> - vfio_device_get_kvm_safe(df->device, df->kvm);
> - spin_unlock(&df->kvm_ref_lock);
> -}
> -
> long vfio_df_ioctl_bind_iommufd(struct vfio_device_file *df,
> struct vfio_device_bind_iommufd __user *arg)
> {
> @@ -99,7 +92,7 @@ long vfio_df_ioctl_bind_iommufd(struct vfio_device_file *df,
> * a reference. This reference is held until device closed.
> * Save the pointer in the device for use by drivers.
> */
> - vfio_df_get_kvm_safe(df);
> + vfio_device_get_kvm_safe(df->device, &df->kvm_ref);
>
> ret = vfio_df_open(df);
> if (ret)
> diff --git a/drivers/vfio/group.c b/drivers/vfio/group.c
> index 610a429c6191..756e47ff4cf0 100644
> --- a/drivers/vfio/group.c
> +++ b/drivers/vfio/group.c
> @@ -157,13 +157,6 @@ static int vfio_group_ioctl_set_container(struct vfio_group *group,
> return ret;
> }
>
> -static void vfio_device_group_get_kvm_safe(struct vfio_device *device)
> -{
> - spin_lock(&device->group->kvm_ref_lock);
> - vfio_device_get_kvm_safe(device, device->group->kvm);
> - spin_unlock(&device->group->kvm_ref_lock);
> -}
> -
> static int vfio_df_group_open(struct vfio_device_file *df)
> {
> struct vfio_device *device = df->device;
> @@ -184,7 +177,7 @@ static int vfio_df_group_open(struct vfio_device_file *df)
> * the pointer in the device for use by drivers.
> */
> if (device->open_count == 0)
> - vfio_device_group_get_kvm_safe(device);
> + vfio_device_get_kvm_safe(device, &device->group->kvm_ref);
>
> df->iommufd = device->group->iommufd;
> if (df->iommufd && vfio_device_is_noiommu(device) && device->open_count == 0) {
> @@ -560,7 +553,7 @@ static struct vfio_group *vfio_group_alloc(struct iommu_group *iommu_group,
>
> refcount_set(&group->drivers, 1);
> mutex_init(&group->group_lock);
> - spin_lock_init(&group->kvm_ref_lock);
> + spin_lock_init(&group->kvm_ref.lock);
> INIT_LIST_HEAD(&group->device_list);
> mutex_init(&group->device_lock);
> group->iommu_group = iommu_group;
> @@ -884,13 +877,6 @@ bool vfio_group_enforced_coherent(struct vfio_group *group)
> return ret;
> }
>
> -void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm)
> -{
> - spin_lock(&group->kvm_ref_lock);
> - group->kvm = kvm;
> - spin_unlock(&group->kvm_ref_lock);
> -}
> -
> /**
> * vfio_file_has_dev - True if the VFIO file is a handle for device
> * @file: VFIO file to check
> diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
> index c26d1ad68105..a1f741365075 100644
> --- a/drivers/vfio/vfio.h
> +++ b/drivers/vfio/vfio.h
> @@ -12,18 +12,23 @@
> #include <linux/module.h>
> #include <linux/vfio.h>
>
> +struct kvm;
> struct iommufd_ctx;
> struct iommu_group;
> struct vfio_container;
>
> +struct vfio_kvm_reference {
> + struct kvm *kvm;
> + spinlock_t lock;
> +};
> +
> struct vfio_device_file {
> struct vfio_device *device;
> struct vfio_group *group;
>
> u8 access_granted;
> u32 devid; /* only valid when iommufd is valid */
> - spinlock_t kvm_ref_lock; /* protect kvm field */
> - struct kvm *kvm;
> + struct vfio_kvm_reference kvm_ref;
> struct iommufd_ctx *iommufd; /* protected by struct vfio_device_set::lock */
> };
>
> @@ -88,11 +93,10 @@ struct vfio_group {
> #endif
> enum vfio_group_type type;
> struct mutex group_lock;
> - struct kvm *kvm;
> + struct vfio_kvm_reference kvm_ref;
> struct file *opened_file;
> struct blocking_notifier_head notifier;
> struct iommufd_ctx *iommufd;
> - spinlock_t kvm_ref_lock;
> unsigned int cdev_device_open_cnt;
> };
>
> @@ -108,7 +112,6 @@ void vfio_device_group_unuse_iommu(struct vfio_device *device);
> void vfio_df_group_close(struct vfio_device_file *df);
> struct vfio_group *vfio_group_from_file(struct file *file);
> bool vfio_group_enforced_coherent(struct vfio_group *group);
> -void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm);
> bool vfio_device_has_container(struct vfio_device *device);
> int __init vfio_group_init(void);
> void vfio_group_cleanup(void);
> @@ -171,10 +174,6 @@ static inline bool vfio_group_enforced_coherent(struct vfio_group *group)
> return true;
> }
>
> -static inline void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm)
> -{
> -}
> -
> static inline bool vfio_device_has_container(struct vfio_device *device)
> {
> return false;
> @@ -435,11 +434,12 @@ static inline void vfio_virqfd_exit(void)
> #endif
>
> #if IS_ENABLED(CONFIG_KVM)
> -void vfio_device_get_kvm_safe(struct vfio_device *device, struct kvm *kvm);
> +void vfio_device_get_kvm_safe(struct vfio_device *device,
> + struct vfio_kvm_reference *ref);
> void vfio_device_put_kvm(struct vfio_device *device);
> #else
> static inline void vfio_device_get_kvm_safe(struct vfio_device *device,
> - struct kvm *kvm)
> + struct vfio_kvm_reference *ref)
> {
> }
>
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index 124cc88966a7..e77e8c6aae2f 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -397,7 +397,7 @@ vfio_allocate_device_file(struct vfio_device *device)
> return ERR_PTR(-ENOMEM);
>
> df->device = device;
> - spin_lock_init(&df->kvm_ref_lock);
> + spin_lock_init(&df->kvm_ref.lock);
>
> return df;
> }
> @@ -1303,7 +1303,8 @@ bool vfio_file_enforced_coherent(struct file *file)
> EXPORT_SYMBOL_GPL(vfio_file_enforced_coherent);
>
> #if IS_ENABLED(CONFIG_KVM)
> -void vfio_device_get_kvm_safe(struct vfio_device *device, struct kvm *kvm)
> +void vfio_device_get_kvm_safe(struct vfio_device *device,
> + struct vfio_kvm_reference *ref)
> {
> void (*pfn)(struct kvm *kvm);
> bool (*fn)(struct kvm *kvm);
> @@ -1311,28 +1312,33 @@ void vfio_device_get_kvm_safe(struct vfio_device *device, struct kvm *kvm)
>
> lockdep_assert_held(&device->dev_set->lock);
>
> - if (!kvm)
> - return;
> + spin_lock(&ref->lock);
> +
> + if (!ref->kvm)
> + goto out;
>
> pfn = symbol_get(kvm_put_kvm);
> if (WARN_ON(!pfn))
> - return;
> + goto out;
>
> fn = symbol_get(kvm_get_kvm_safe);
> if (WARN_ON(!fn)) {
> symbol_put(kvm_put_kvm);
> - return;
> + goto out;
> }
>
> - ret = fn(kvm);
> + ret = fn(ref->kvm);
> symbol_put(kvm_get_kvm_safe);
> if (!ret) {
> symbol_put(kvm_put_kvm);
> - return;
> + goto out;
> }
>
> device->put_kvm = pfn;
> - device->kvm = kvm;
> + device->kvm = ref->kvm;
> +
> +out:
> + spin_unlock(&ref->lock);
> }
>
> void vfio_device_put_kvm(struct vfio_device *device)
> @@ -1353,6 +1359,21 @@ void vfio_device_put_kvm(struct vfio_device *device)
> device->kvm = NULL;
> }
>
> +static void vfio_device_set_kvm(struct vfio_kvm_reference *ref,
> + struct kvm *kvm)
> +{
> + spin_lock(&ref->lock);
> + ref->kvm = kvm;
> + spin_unlock(&ref->lock);
> +}
> +
> +static void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm)
> +{
> +#if IS_ENABLED(CONFIG_VFIO_GROUP)
> + vfio_device_set_kvm(&group->kvm_ref, kvm);
> +#endif
> +}
> +
> static void vfio_device_file_set_kvm(struct file *file, struct kvm *kvm)
> {
> struct vfio_device_file *df = file->private_data;
> @@ -1362,9 +1383,7 @@ static void vfio_device_file_set_kvm(struct file *file, struct kvm *kvm)
> * be propagated to vfio_device::kvm when the file is bound to
> * iommufd successfully in the vfio device cdev path.
> */
> - spin_lock(&df->kvm_ref_lock);
> - df->kvm = kvm;
> - spin_unlock(&df->kvm_ref_lock);
> + vfio_device_set_kvm(&df->kvm_ref, kvm);
> }
>
> /**