Re: [PATCH v5 11/13] KVM: s390: implement mediated device open callback

[Pierre Morel <pmorel@linux.ibm.com>]

On 07/05/2018 17:11, Tony Krowiak wrote:
> Implements the open callback on the mediated matrix device.
> The function registers a group notifier to receive notification
> of the VFIO_GROUP_NOTIFY_SET_KVM event. When notified,
> the vfio_ap device driver will get access to the guest's
> kvm structure. With access to this structure the driver will:
>
> 1. Ensure that only one mediated device is opened for the guest
>
> 2. Configure access to the AP devices for the guest.
>
>     Access to AP adapters, usage domains and control domains
>     is controlled by three bit masks contained in the Crypto Control
>     Block (CRYCB) referenced from the guest's SIE state description:
>
>     * The AP Mask (APM) controls access to the AP adapters. Each bit
>       in the APM represents an adapter number - from most significant
>       to least significant bit - from 0 to 255. The bits in the APM
>       are set according to the adapter numbers assigned to the mediated
>       matrix device via its 'assign_adapter' sysfs attribute file.
>
>     * The AP Queue Mask (AQM) controls access to the AP queues. Each bit
>       in the AQM represents an AP queue index - from most significant
>       to least significant bit - from 0 to 255. A queue index references
>       a specific domain and is synonymous with the domian number. The
>       bits in the AQM are set according to the domain numbers assigned
>       to the mediated matrix device via its 'assign_domain' sysfs
>       attribute file.
>
>     * The AP Domain Mask (ADM) controls access to the AP control domains.
>       Each bit in the ADM represents a control domain - from most
>       significant to least significant bit - from 0-255. The
>       bits in the ADM are set according to the domain numbers assigned
>       to the mediated matrix device via its 'assign_control_domain'
>       sysfs attribute file.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
> ---
>   arch/s390/include/asm/kvm-ap.h        |   21 ++++++++++
>   arch/s390/include/asm/kvm_host.h      |    1 +
>   arch/s390/kvm/kvm-ap.c                |   19 +++++++++
>   drivers/s390/crypto/vfio_ap_ops.c     |   68 +++++++++++++++++++++++++++++++++
>   drivers/s390/crypto/vfio_ap_private.h |    2 +
>   5 files changed, 111 insertions(+), 0 deletions(-)
>
> diff --git a/arch/s390/include/asm/kvm-ap.h b/arch/s390/include/asm/kvm-ap.h
> index 21fe9f2..68c5a67 100644
> --- a/arch/s390/include/asm/kvm-ap.h
> +++ b/arch/s390/include/asm/kvm-ap.h
> @@ -83,6 +83,27 @@ struct kvm_ap_matrix {
>   bool kvm_ap_instructions_available(void);
>
>   /**
> + * kvm_ap_refcount_read
> + *
> + * Read the AP reference count and return it.
> + */
> +int kvm_ap_refcount_read(struct kvm *kvm);
> +
> +/**
> + * kvm_ap_refcount_inc
> + *
> + * Increment the AP reference count.
> + */
> +void kvm_ap_refcount_inc(struct kvm *kvm);
> +
> +/**
> + * kvm_ap_refcount_dec
> + *
> + * Decrement the AP reference count
> + */
> +void kvm_ap_refcount_dec(struct kvm *kvm);
> +
> +/**
>    * kvm_ap_configure_matrix
>    *
>    * Configure the AP matrix for a KVM guest.
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 8736cde..5f1ad02 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -717,6 +717,7 @@ struct kvm_s390_crypto {
>   	__u8 aes_kw;
>   	__u8 dea_kw;
>   	__u8 apie;
> +	atomic_t aprefs;
>   };
>
>   #define APCB0_MASK_SIZE 1
> diff --git a/arch/s390/kvm/kvm-ap.c b/arch/s390/kvm/kvm-ap.c
> index 98b53c7..848fb37 100644
> --- a/arch/s390/kvm/kvm-ap.c
> +++ b/arch/s390/kvm/kvm-ap.c
> @@ -9,6 +9,7 @@
>   #include <linux/kernel.h>
>   #include <linux/bitops.h>
>   #include <asm/kvm-ap.h>
> +#include <asm/atomic.h>
>
>   #include "kvm-s390.h"
>
> @@ -218,6 +219,24 @@ static int kvm_ap_validate_queue_sharing(struct kvm *kvm,
>   	return 0;
>   }
>
> +int kvm_ap_refcount_read(struct kvm *kvm)
> +{
> +	return atomic_read(&kvm->arch.crypto.aprefs);
> +}
> +EXPORT_SYMBOL(kvm_ap_refcount_read);
> +
> +void kvm_ap_refcount_inc(struct kvm *kvm)
> +{
> +	atomic_inc(&kvm->arch.crypto.aprefs);
> +}
> +EXPORT_SYMBOL(kvm_ap_refcount_inc);
> +
> +void kvm_ap_refcount_dec(struct kvm *kvm)
> +{
> +	atomic_dec(&kvm->arch.crypto.aprefs);
> +}
> +EXPORT_SYMBOL(kvm_ap_refcount_dec);

Why are these functions inside kvm-ap ?
Will anyone use this outer of vfio-ap ?

> +
>   int kvm_ap_configure_matrix(struct kvm *kvm, struct kvm_ap_matrix *matrix)
>   {
>   	int ret = 0;
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 81e03b8..8866b0e 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -11,6 +11,8 @@
>   #include <linux/device.h>
>   #include <linux/list.h>
>   #include <linux/ctype.h>
> +#include <linux/module.h>
> +#include <asm/kvm-ap.h>
>
>   #include "vfio_ap_private.h"
>
> @@ -47,6 +49,70 @@ static int vfio_ap_mdev_remove(struct mdev_device *mdev)
>   	return 0;
>   }
>
> +static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
> +				       unsigned long action, void *data)
> +{
> +	struct ap_matrix_mdev *matrix_mdev;
> +
> +	if (action == VFIO_GROUP_NOTIFY_SET_KVM) {
> +		matrix_mdev = container_of(nb, struct ap_matrix_mdev,
> +					   group_notifier);
> +		matrix_mdev->kvm = data;
> +	}
> +
> +	return NOTIFY_OK;
> +}
> +
> +static int vfio_ap_mdev_open(struct mdev_device *mdev)
> +{
> +	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> +	unsigned long events;
> +	int ret;
> +
> +	if (!try_module_get(THIS_MODULE))
> +		return -ENODEV;
> +
> +	matrix_mdev->group_notifier.notifier_call = vfio_ap_mdev_group_notifier;
> +	events = VFIO_GROUP_NOTIFY_SET_KVM;
> +
> +	ret = vfio_register_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
> +				     &events, &matrix_mdev->group_notifier);
> +	if (ret)
> +		goto out_err;
> +
> +	/* Only one mediated device allowed per guest */
> +	if (kvm_ap_refcount_read(matrix_mdev->kvm) != 0) {
> +		ret = -EEXIST;
> +		goto out_err;
> +	}

Testing the existence should be the first thing to do.

> +
> +	kvm_ap_refcount_inc(matrix_mdev->kvm);
> +
> +	ret = kvm_ap_configure_matrix(matrix_mdev->kvm, &matrix_mdev->matrix);
> +	if (ret)
> +		goto config_err;
> +
> +	return 0;
> +
> +config_err:
> +	kvm_ap_refcount_dec(matrix_mdev->kvm);
> +out_err:
> +	module_put(THIS_MODULE);
> +
> +	return ret;
> +}
> +
> +static void vfio_ap_mdev_release(struct mdev_device *mdev)
> +{
> +	struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
> +
> +	kvm_ap_deconfigure_matrix(matrix_mdev->kvm);
> +	vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
> +				 &matrix_mdev->group_notifier);
> +	kvm_ap_refcount_dec(matrix_mdev->kvm);
> +	module_put(THIS_MODULE);
> +}
> +
>   static ssize_t name_show(struct kobject *kobj, struct device *dev, char *buf)
>   {
>   	return sprintf(buf, "%s\n", VFIO_AP_MDEV_NAME_HWVIRT);
> @@ -773,6 +839,8 @@ static ssize_t matrix_show(struct device *dev, struct device_attribute *attr,
>   	.mdev_attr_groups	= vfio_ap_mdev_attr_groups,
>   	.create			= vfio_ap_mdev_create,
>   	.remove			= vfio_ap_mdev_remove,
> +	.open			= vfio_ap_mdev_open,
> +	.release		= vfio_ap_mdev_release,
>   };
>
>   int vfio_ap_mdev_register(struct ap_matrix *ap_matrix)
> diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
> index 8b6ad66..ab072e9 100644
> --- a/drivers/s390/crypto/vfio_ap_private.h
> +++ b/drivers/s390/crypto/vfio_ap_private.h
> @@ -32,6 +32,8 @@ struct ap_matrix {
>
>   struct ap_matrix_mdev {
>   	struct kvm_ap_matrix matrix;
> +	struct notifier_block group_notifier;
> +	struct kvm *kvm;
>   };
>
>   static inline struct ap_matrix *to_ap_matrix(struct device *dev)


-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany